Well, I promised I wouldn't speculate until there was something solid about Project Needlemouse to speculate about.
There are now three more certainties about the game, and I'll be looking at each (briefly) in turn.
1.) Sonic is the only playable character
I am disappointed that Tails and Knuckles won't be playable, even optionally, but on the other hand I'm happy to know that we won't be forced to play as any characters that I don't like.
However, I want to point out that, technically, Sonic Unleashed didn't have any playable characters besides Sonic, either, and that didn't save it. We were still saddled with new (and unpleasant) gameplay gimmicks that broke up the action and padded out the game.
Finally, this whole character countdown seems to be about playable characters and playable characters only. For all I know right now, Shadow and Big and the whole goon platoon will be making NPC appearances. While that's better than having to shift their girth around myself, I'd still like to know that they won't be making an appearance at all. It would be nice to be assured that there will be no Amy glomping, Shadow angst, or Big inanity even in the cutscenes. Alas.
2.) There will be no new characters introduced, playable or otherwise
This suggests that the game will either be light on story altogether (it's hard to tell a story without characters), or concentrate on the classic characters more. This screams "remake" to me, but the original teaser did say "all new adventure", so we'll see.
3.) Classic Badnik, Shellcracker
Shellcracker, or "Kani Punch" (Kani is japanese for crab) concept art
It's about time we saw some classic Badniks make a return! This is the first time a major modern Sonic game will use a classic Badnik design, as opposed to enemies that are merely reminiscent of the earlier games.
This is a very good thing. One of my biggest complaints with Sonic Unleashed was the repititious and uninspired enemies, copied and pasted between the levels. Even if the Needlemouse team does nothing else right, this is a step in the right direction.
I also happen to like the concept art very much. It is, above all, incredibly faithful to the original Totoya design, adding detail but not sacrificing the personality. If the same holds true for the rest of Needlemouse, I will be one happy gamer.
I freely admit that the following is wishful thinking, but I have a theory (in the colloquial sense) that they showed concept art of a Badnik - instead of say, Sonic - for a specific and devious reason.
They aren't ready to reveal what Sonic is going to look like yet.
There has been much speculation about whether Sega is going to do the marketable thing and use the modern, green-eyed, lean Sonic design (which, for the record, I think is hideous - I even prefer the European Sonic 3 boxart to this modern floppy monstrosity), or please the retro fanbase and use the classic, round-bellied, short-spined one.
I contend that it is a very real possibility that they may use neither, but instead introduce a brand new overhaul of Sonic's design. After all, they've done it once, and ten years on it's wearing pretty thin. There's nothing to say they won't do it again, and surprise all of us. I mean, if it was just gonna be Olypmic Games / All-Star Racing Sonic, why haven't we seen hide nor spine of him yet? It's a thought.
Well, that's it for Needlemouse speculation from me until something else of substance pops up. Here's hoping they don't make us wait until E3 for the next titbits.
P.S. I've gone and done it now, I've made a Project Needlemouse Excitement Meter (see the sidebar to the right). The percentage is in comparison to how excited I was about Sonic & Knuckles' imminent release (which was about as stoked as any human can get). The value will change as new info comes in.