I don't think limewire is used that much anymore although I could be wrong. I try to use it but the file selection is so poor IMO.
Torrents are in right now.
I think the biggest shifts were:
Napster -> Morpheus and Kazaa -> Limewire -> Torrents
Although torrents have been around for a little longer, they haven't gained popularity until just these past couple years. eDonkey/eMule has been in the background for a long time but I don't think it has ever been #1.
What do you guys think the major clients have been?
Getting back to the future, like all kingdoms, the torrent one will fall eventually. I don't think anyone knows what's going to be next.