Generally, it's true that the first character in a wave of Smash newcomers does signal a greater theme in that wave of newcomers:
- Adding characters that did well in the Smash 2 poll, while also experimenting with unconventional choices for a fighting game.
- Filling out the casts of the series already in Smash.
- Giving the spotlight to both Nintendo franchises without characters and characters gained relevance after Brawl's release.
- Bringing back cut veterans and showcasing big, iconic characters.
- Adding fan favourites that were highly requested among the core fanbase.
- Introducing more third parties that hail from generally smaller franchises that what had been seen before.
However, the important thing to note as that
all of these themes can only be seen in hindsight. We can't say that Meta Knight is part of the theme of adding supporting characters without confirming that theme through additions like Diddy Kong, Zero Suit Samus, and King Dedede. Likewise, it's very easy to assume that because
the first character fits this theme, those that follow must also fit the theme, when that's not true. Many thought Inkling would signify that we'd see more modern Nintendo characters like Rex, when that didn't happen. Likewise, many assumed that Joker's inclusion would also mean that the Fighter's Pass would mostly (or entirely) be recently created third parties with limited Nintendo connections. The following three third parties were all legacy characters, with 2 have strong historical ties to Nintendo and the third recently connecting with the Big N in the Switch's early days.
So, what does this mean for ARMS and Smash Speculation? ARMS likely does represent
some greater theme for the roster, but we have no idea what that pattern that is. The ARMS character could be part of a trend of upgrading assists, upgrading spirits, generally more Nintendo, a greater emphasis on Switch content, and many more possible ideas. Alternatively, it could be multiple of these or none of these. The beginning of a speculation period requires a lot of guess work this early in the game. As such, I think proposing "big leap" characters that require certain conditions to be valid is fine and should be worth discussing beyond saying "yeah, but you're just assuming that". At the same time, nothing is guaranteed (beyond ARMS, of course), so hyping responsibly and not becoming permanently wed to certain ideas is also important.