Smallville is kind of falling to pieces these days.
Kristin Kreuk is coming back for only a few episodes and Michael Rosenbaum is done.
Unfortunately, though, things might not be ending here. Though Allison Mack (Chloe) was rumored to be coming back, she still had not (and has not) signed a new contract. Furthermore, it seems that with all of the other characters leaving, she wants more $$ (she kind of deserves it, no?) and thus far no agreement has been reached.
As one source points out, "They need Chloe now more than ever - and Allison's people know it."
Let's hope something gets worked out, as Season 8 of Smallville is looking more pathetic with each passing day...