This was in the latest issue of SFX magazine:
Yours Faithfully
Will Angel see the return of our second favourite Slayer? Eliza Dushku certain hopes so...
This season of Angel, the show's fifth, was supposed to be marked by return appearance by Sarah Michelle Gellar as Buffy Summers and Eliza Dushku as Faith. Sadly, it's not going to happen. Despite comments to the contary last season, Gellar simply decided to bail out, wanting to distance herself from her vampire-slaughtering alter ego. For Dushku, it genuinely was a question of time.
"I've never ruled out a return to the show," she says, "I said I would return to the show before I got here and realised the workload. I haven't had the time, but I've always said that I love those guys and if I had any time at all I would love to go down and hang out with my peeps on Angel." Fingers crossed...