There were a couple other interesting things in this update, especially if you look closely at some of the events in the first two pictures. I'll start off with the first picture, and list the events.
First One: Trouble Kings. We know about this one. It has (in my opinion) strengthened the starting roster theory, because it looks like all three Kirby characters are characters you'll start with. Other than that? Nothing new.
Second One: All we get out of this is that it involves the Landmaster Tank. Nothing really interesting here.
Third One: This one implies something else quite important. This one has you playing as Meta Knight, meaning I'm betting a 99% chance he's in the starting roster, as there was never an event you could play as a character you didn't have yet.
Fourth One: This one was announced in the original announcement for Event Modes. It involves Pit and Wario, and is not the same is the fourth event from Co-Op at all. Not much to say.
Fifth One: This is pokemon trainer in what appears to be the pokemon arena. What does this mean? Well, from the picture it's hard to tell, but I think it's fairly safe to assume that it's similar to co-op event two.
Sixth One: This one... I have no idea. When I first looked at it I thought of the moon from Majora's Mask, but I'm hugely biased, and upon further inspection, I don't think that's it at all. However, all I can say is that it looks to take place in some sort of Jungle. A DK event, perhaps? It's way too hard to tell, and I'm sure a couple million people will ask about it later.
Then we go to the Co-Op events.
Co-Op one: Two Trouble Kings... simply amazing. Yeah, does anything really need to be said?
Co-Op two: The picture looks like some sort of green dragon fighting an Ivysaur on Pokemon stadium 2, and in the list of co-op events that was the second one listed, Pokemon trainers fighting each other... So you know what? I'm going to go ahead and say that green dragon is an alt. colour for Charizard. Also, in the actual picture for the event, you can see Pokemon Trainer wearing green while a green Ivysaur is on the field. It's notable as the first alt. colour for Pokemon Trainer, and, well, it reveals how the alt-colours for his Pokemon will work... they take a common colour.
Co-Op three: Defeat the most enemies in 10 seconds! Yeah, at first glance not much to say here... Until you realize that they're using King Dedede. That early on? Considering I doubt you'll have to unlock Co-Op event and you never had to play the first event first, I'm fairly certain that confirms King Dedede is in the starting roster, although there is a small chance he won't be. Still, things look good for the King, and the roster theory.
Co-Op four: Is it just me, or does the picture for Co-Op four look completely different from All Mine? The picture looks like some golden star on a tropical island. When I first looked at it, I thought 'Stafy', and seeing how he is an AT that can be hurt, it would certainly be interesting to have an event match with him. The listed event is entirely different, however, which breaks the pattern. However, I'm going to explain why later. Right now, I want to get to...
Co-Op five: So, this is interesting. It is Eldin Bridge, no doubt about it. And it has two dark characters involved. Looking immediately at the two, you can assume one is Dark Link, but who is the other? After a minute of looking at it, it's Samus, except Dark. Dark Samus? I'm jumping to a huge conclusion here, saying that just because a dark version of samus exists Dark Samus won't be in, but considering Sakurai's stance on the Prime series, it's not too unlikely. I sincerely hope it isn't though, because it bodes ill for any good prime representation. However, the fact remains that it looks like in this event you fight Dark Link & Samus on the Bridge of Eldin. This lends strength to the relationship between Co-Op 2 and Event 5, which appear to be the same as well, because Regular Event 5 is the PT battle, opposed to the battle with 'Dark' characters.
Co-Op six: This looks like Zero Suit Samus and Zelda behind her, in some stage I cannot make out. It doesn't look too much like any stage before it, but if it is a new stage, there is no chance we can tell anything about it by such a small, useless photo. As for the choice of characters, it might simply be because they are female, like the Femme Fatale event match in Melee, but they also share another possible trait... transforming characters? It is possible, but it is way too much of a stretch for me to make. But that's all I can get on that.
So, what about All Mine & the fourth Co-Op event match? This is the same case as 'Sleeping in the Eggs' and 'Dark Link Duel' in the Event update; not shown, and probably events that will occur somewhat later. The reason All Mine was specifically chosen was because it makes a nice lead in to coin battles, the other half of the update.
And on a final note: Why does the new Target Test look so terrible? Why? What are they thinking? So far it looks awful.
So, in conclusion, this update strengthened the idea that the current roster with the exceptions of Snake & Sonic is the starting roster, possibly -1 if they decide to put another first party in as the newcomer. I think, however, that the last newcomer spot is for another 3rd party, and we have our starting roster. I won't comment on Dark Samus. I'll let that one up to you to decide, whether it hurts her chances or not. All in all, more to that update than expected.