From TV Guide Online:
TVGO: Given that Buffy’s death factored into Angel’s finale, won’t you have to kick off the season with some type of WB/UPN crossover?
Whedon: No, I really won’t. And I’m not entirely sure that either network would want to. Not that Angel won’t be dealing with the idea of Buffy’s death and her rebirth, but the fact is, he’s on his own now. He’s at the big scary network by himself and he’s going to have other very pressing matters to deal with.