1. Nothing fundamental is going to happen to improve the picture quality. Such improvements as we will see in the future will be due to slightly better chips, processing, etc., and not anything in the spec being improved.
2. The new lossless sound formats will be completely supported, but this will in practice not make that much of a difference. Current PCM soundtracks on many Blu-ray disks are excellent.
The changes will all be to interactive features, internet connections, etc.
My point: I don't think that delaying to wait for these features is much warranted.
There are better reasons to wait (probably the largest being the remaining uncertainty about the outcome of the format war itself). I am telling my friends that I think it is a 70% chance that Blu-ray will win but no one I have told that to has gone out and bought a player on that basis, so waiting for the format war to be over is very popular in my group anyway.