Ok, first of all, I think people are looking at the wrong screen for sonic. But, it's hard to tell with that blue smudge. So, let me show you where I believe you have to look.

If you look at the screen closely, even with it shrunk down as it is, you can see what looks to be Sonic's spiky hair. Also, there appears to be an eye that looks like it would belong to Sonic. It's got a lot of white and the dot pupil. Or it could just be people trying to see what they want out of the photo. But, if anyone is still confused about Sonic. I believe that's what you should be looking at.
Second, I actually wouldn't complain that much if online wasn't in the game. I am happy with what I have seen so far for the single player. I know Smash_Brother has asked who plays the single player more than the multiplayer. Well, I guess I am the answer. I was looking at my data record and noticed that I've spent two more hours playing single over multiplayer.
Third, now I know the reason for the existance of assist trophies. They've been added to make some use for the character models that are being put into the single player mode. Think about it. We've seen Hammer Bro as an assist trophy and now there's a picture of him fighting Fox McCloud. You think Knuckle Joe is going to be an opponent in the Kirby world? Of course. Don't forget the first assist trophy, Samurai Goroh. If they have bosses for these single player worlds, chances are he's the boss of the F-Zero world. Of course, I'm not sure how Dr. Wright from Sim City would fit in but it's possible he's used in the single player mode also.
Fourth. I for one believe that the reason Nintendo is being tightlipped on the online for brawl is because they are going to go all out on it. I think of the way Sakurai puts in data trackers. There is all the different data results you can see in Melee like KO numbers, time spent playing, stuff like that. Meteos for the DS also had something similiar. So, it's possible Sakurai has a huge online system planned. However, not everything may be able to work for it or be finished in time. So by staying tightlipped, Nintendo doesn't promise something that may not happen. Think about it this way. If Nintendo said, yes, there is online play, there will be 1 vs 1, 4 player melee, etc, well then people would keep asking for details on how this will work or if this will be put in. Will there be leaderboards? Can we make online tournaments?
But by not even saying anything about online, everyone is instead just focused on asking if there will be online. Then, when Nintendo is ready, they announce it's online and what all the online features are and can start discussing and answering what is possible and what isn't. I think it's just a matter of waiting and finalizing. You look at Strikers. People knew it was online but that just raised a whole bunch of questions and confusion about how the online worked. Was there international play or just national play? How do you find opponents? Are there friend codes or not? Just stating it was online was not enough.
Just my thoughts though.