IMHO, I think most of us expect it to be way bigger than LBP.
PS: quick question about LBP (I already asked in the What are you playing now? thread, but nobody replied yet): which one of the three iterations is best for 2 players gameplay (with the same console, at the same time)? Thank you!
Why do you expect Dreams to be bigger? Most people only consume content and do not produce it. And it seems "harder" to make something in Dreams.
As for LPB, I think I played nr 1 and 2, but I seem to recall there was always the option of 4 players as long as you had enough controllers. Now if some maps/levels was better for co-op in 1 or 2 I have no idea.