Putting Lemmings on the PSP seemed like a logical move. A full-price puzzle game for the PC is pretty difficult to push into the market nowerdays, I think. You might find real puzzler gems in the bargain bin of a computer store, but that's often scratchware done by smaller companies.
It's not that likely, but if Sony is going to release another big Lemmings game on the PC, I hope they don't alter too much. I like L2 very much, but even I would be sceptical about tons of new skills or game mechanic twists these days. ;-)
I don't follow the Lemmix/Lemmini community that well - I did play ccexplore's awesome port of the Genesis levels, but that's it been for me until now, in spite of several clever level designers out here. In my opinion, however, such community-driven games are the very best way to keep Lemmings alive at its core. :-)
-- Simon