A bit of both, actually.
Waning only because I miss some of the games I used to play (don't have time for more than one concurrent game). I've got an itch to play in the World of Darkness.
I've always liked Mage. I haven't tried Hunter and I've got at least one player who has owned the book since it was released and hasn't read a word of it because I told him I thought it'd be more fun to come in ignorant. Also, after a recent discussion on these boards, I want to give Werewolf a real try. Finally, even before 3E came out, I'd started working on a massive crossover game with a great (IMHO) story arc, but never got around to starting it before 3E came out.
Waxing in general, though. When I dropped 2E back circa 1993, I vowed never to go back to a class/level-based system -- even going so far as to get rid of all system-specific development on my (then) ten year old home-brew world.
Man, was that dumb. I absolutely love the simplicity of the d20 system. The new multiclass rules allow for a wide range of character concepts. Trading to a different system would only be a trade-off of shortcomings. About the only thing that still bugs me is the horrendous Vancian magic system, but that's a topic in itself.