If you did a search you'd have already been given this answer:
SEPTEMBER.
That's when Apple usually does the major iPod refresh, and I wouldn't expect the 3rd gen any sooner. Yes, the 3.0 software and the new iPhone are apparently coming out June-ish (well, summer anyway), but the iPod touch will, most likely, be kept until September, just like last year and the year before.
September? IMHO it's going to be July from what I hear and read.
And sure, definitely wait for iPod refresh.