To be clear, the characters in that image who have not been shown to be in the game so far:
Marth
Meta Knight
Luigi
Wario
Mr. Game & Watch
Zero Suit Samus
The image also contains a pikmin, a Mr. Saturn, Sandbag, a Heart Container, a star of some sort (Warp Star?), and what appears to be but is kinda ambiguously Master Hand in the background. Either way, this image hasn't been said to confirm anything directly, but I'd feel pretty good about the inclusion of elements from the picture since it would be very odd for Sakurai to show characters in concept art that he didn't plan to include (just like how Lucas's dojo reveal effectively confirmed Ness; Sakurai never would have mentioned Ness on the dojo if Ness was not going to return just like he never mentioned Mewtwo, Roy, Pichu, or Dr. Mario).
I'd also like to repeat that, if your current Brawl main gets cut, it's not the end of the world. I feel pretty good about G&W's chances of returning, but I'd live if he were gone. I already really like how Mega Man looks (and the Villager to a lesser extent), there are several other characters in Brawl I liked anyway who may be tweaked in ways that I'll love in smash 4, and who knows what else we're going to see? Even if G&W does return, I might not play him in smash 4 anyway so there's no reason for me to get hung up on his inclusion. It will make this next year of a slow drip of information far less stressful on you if you take the same attitude I am taking.