Oh yeah, this topic is now more relevant then ever given we don't quite know the status of the upcoming game completely.
My stance is still this game will be a bit of a compromise. A majority of if not all of the characters will return. With some getting tweaks here and there but otherwise stay mostly faithful to how they were in previous games. This will come at a cost of likely a much smaller number of Newcomers in the main game then we may be used to. But they'll make up for it with a longer period for DLC.
Nintendo will still market it as if it's a brand new game, and there will be plenty of new content that may very well make it at least arguable enough to count. But generally the feel in terms of way most of the characters handle, the graphics, gameplay, and at least most of the stages will feel more familiar with Smash 4 then any transition between a new game.
There may be moments that will feel cookie-cutter from Smash 4. But it won't feel so bad when you compare it to say all those franchises that release yearly games that are just about the same thing but with maybe one new mode and a roster update like the EA Sports games or the Call of Duty titles. It won't be a reboot of the franchise that some in the minority kind of want (Though I understand why people would say Smash Bros. character rosters have become too bloated) either as much as that might sharpen the core of the game. But that's if the game was geared just for the hardcore fighting game base rather then encompassing all kinds of fans of not just fighting games, but fans of nintendo in general, people playing video games for the first time, etc. and all that kinda calls for a large roster to try to appeal to many. Cause you want to make longtime players happy to see their character back, as well as attract new fans with more recent characters too. So if Smash Bros. was meant to encompass many types of fans, this was the natural direction it must take.