Considering that all the games on All-Stars have already been ported to the GBA (except SMB1, which was done on the GBC. I don't think the Lost Levels have been ported either) I would doubt that this game would contain all of those games. What I do think is going on is that Nintendo is taking elements of those games, and mixing them into the SMB3 world. Either added to the old levels, or added as bonus levels. It may even be the case that my idea from several months ago of a SMB3 with an entirely new world/set of worlds might be coming our way. Think about it. You beat Bowser in World 8, and instead of going to credits there is some sort of little cut scene, and then you go to World 9! The extra worlds would have elements of SMB2 and SMW in them. Like the turnips and the cape. Yoshi would get in on the action as well. As long as there is an option to play the original levels they could even add these things to the current set of SMB3 levels. It would change how the game was played, making for my replay value.
This would also feed everyone's need for a new Mario game on the GBA, but would be even better because you would be getting the best mario game along with it, and it would play very similar to the best.
What I really want to know is if the Comunication option that PGC said was disabled in the demo does. Is it just for playing link battles? Perhaps there is something else it can do. You could do a set up where one play is Luigi, and the other is Mario. Players would play the same level at the same time and have to race to the finish. The winner (either by time or coins collected) would then get to control the overworld and and pick the next stage. This would be such a freaking cool feature.