Actually I think HS is a good case. The issues with Hearthstone are:
1. The RNG nature. SSB does not have this apart from a few RNG based moves and when/what items spawn.
2. Based on point 1, you can have overpowered card combos. They only occur right 1 in 10-20 matches but when they do it';s insta lose for the other player. hearthstone does not have this either.
3. Blizzard thinks an overused card is unbalanced and nerfs cards based on this. In a way Blizzard still do not know how to balance a card game properly. Blizzard fail to understand how point 2 here can totally wreck card games.
Despite all of this HS is pretty well balanced as a game. SSB on the other hand won't have the RNG factor but it will have some moves used a lot more than others and hard counters to certain moves and character/stage choices. And when they are known, there's not much you can do about it. You just choose the counter to what you think you'll vs VSing. It'll be a science. You guess what moveset/character you'll vsing and what stage that'll be on and based on that you'll chose a counter. The same moveset/character/stage will have the same counter every time. It will never change. Unless there are patches that update/change the characters or moves or stages. Blizzard does these hard changes and this forces the meta to change and adapt to the changes. SSB with none of these patch changes (I assume) won't have any of these changes for the meta to react to. So once the initial meta is worked out, it won't change unless something in learnt about the game that no one knew before.
Except that Blizzard having to constantly release balance patches isn't an organically evolving meta, it's a forced one. Overpowered deck A doesn't wane in popularity because people learn how to put basic counters to it in their deck without completely changing their deck, Overpowered Deck A wanes in popularity because Blizzard gives a hard nerf to a card that usually was poorly designed in the first place. One of the biggest reasons for this is that Hearthstone has a LOT of cards that have exponential effects. It's legitimately hard to balance a card like this, and Hearthstone tends to favor towards the way too powerful side of things. Unleash the hounds was a pretty infamously bad example of this. There wasn't a lot of counters to it. You were basically limited to not summoning a lot of monsters when playing a ranger, which if you didn't specifically have a beatstick deck, wasn't a terribly great position to be in.
That said, just because a game has limited complexity (and the term limited here is a bit underwhelming when <3 pointed out that it would take almost a century to test all of the match-ups), doesn't mean that it has a limited metagame. This one is a bit hard to explain though. So, I'll give it my best shot here...
The famous Spanish writer has this story called, "The Library of Babel". In it, a group of people find a library that contains every single possible permutation of a 400 page book that can be written. The number of books is astronomically large, but it's a finite number, and it, by traditional definitions, contains all of knowledge. Of course, this is mostly useless as the books are 99.999999999999...% gibberish and of the ones that do make sense, most of those are flat-out inaccurate or small differences from other books (Like the version of Hamlet where Hamlet sees his father's ghast). However, keen thinkers have pointed out that the information in the library is actually infinite due to contextualization.
The most obvious first reason here is that knowledge isn't always capable of being portrayed in only words. However, the second, and more relevant reason for the knowledge in the library not being limited is because the works themselves can reference themselves. For instance, Book #1059839 might initially seem to be gibberish, but Book #9583 actually explains that this book is encoded with messages and gives you instructions to crack them. In fact, this code is not only relevant to Book #1059839, but several of them that have the same certain sequences of gibberish in them. Once decoded, one of these books itself may explain or change some fact in a completely different book, and the re-contextualization of THAT book drastically changes the meaning of another one somewhere. This keeps going until you actually manage to change the meaning of the original book that told you to decode the first set of books. It goes in an infinite loop.
Of course, most of the books are still useless and no one would live long enough to even get to the point where they were discovering these codes, but the whole thing is a thought experiment. It points out how something with finite resources can actually have a non-finite number of solutions. It merely requires that the thing in question reach enough content and complexity. With a century of match-ups to try, it's fairly safe to say that this'll probably reach that level. That's how an evolving meta-game works. Discoveries made later in the meta-game re-contextualize our understand of some things we thought we understood earlier. The discovery of a new advanced technique will drastically change which characters will be high tier and potentially promote some that we thought were initially garbage. That, in turn, will also increase the popularity of even weaker characters that act as a good hard counter for these more over-used ones.
You actually almost saw this effect in Melee actually, but it just didn't have enough content to create the loop. Still, the metagame has evolved a LOT since when the game was first introduced. There are entire techniques and combos that were popular 3 years ago that are not even viable for most people anymore. While the makeup of which characters are played hasn't changed much, how they're played has changed a lot. Brawl didn't see this, because, while it had more options, it didn't see as strong of a competitive atmosphere AND it had a runaway character that was just objectively better than most of the cast in some pretty important ways. However, this game not only seems more competitively focused overall, but it actually has enough content and characters that the idea of a character not having a good hard counter this time around is pretty astronomically low (The odds of a runaway OP character actually decreases as the number of characters increases. Brawl was somewhat of a fluke in this sense).
So, yeah. Barring the fact that, with the ridiculous size cast here, I wouldn't count on us learning the full set of match-ups anytime soon, that still doesn't mean that the metagame is going to stagnate. The rise in popularity of some characters will inherently necessitate the need to come up with counters for them, and we're likely going to have the tools available to find something for that with or without balance patches.