I have a Ti4600 and it seems perfectly good to me and I hadn't really thought about replacing it until next year some time.
I'm in the same boat, with a 4600. I wouldn't MIND a newer card, but nothing I've seen so far seems to justify the need for an upgrade. Everything I've been playing lately (Jedi Academy, Rise of Nations, Vice City, EF2, IL2, etc.) runs fine.
For me, until I see a definite reason, I can't see just buying a new card. That could be HL2, Doom3, or DX2, but until I get them home and see bad frame rates on what I have now, I'm not going to worry about it. Sure, there's always something out that will give you an extra 10fps, but is it worth $300+ dollars?
Supporter of the "A fredster By Any Other Name Is Still The Same" fan club.http://www.nin.com