Well, HD technology should be perfect now, it will take a while for the broadcasters to catch up.  Consider that up until about 10 years ago, TV had mono sound only, then they added Stereo, but most studios were probably still mono for a long time, some may still be.  Now they mostly have stereo speakers in their control rooms, they may not have 5.1 and that may take a while to get right.  Considering that the number of 5.1 TV's is probably well under 1% of the total, it will be years before it really matters. 

There are two kinds of TV users, those on cable/satellite and those on OTA.

Cable/Sattellite, probably over 90% of all viewers.  With cable set top boxes required for HD cable channels whether you have an HD capable TV or not, because the cable companies charge extra for digital channels, there is no real need for that to change, cable can feed you an analog copy of a digital channel as easily as an analog one.   There is no reason to have a digital TV if your getting an analog copy from your cable company, because you don't want to spend another $17.50/month for the digital TV package.   I expect that once the digital conversion is complete the cable companies will reverse that aspect, in that they will give you the digital channels for free and charge extra for analog, because only 20% of their customers have digital, and they are a greedy lot.

For OTA users, I expect that when the digital conversion happens, most will buy new TV's.  If a digital conversion box is $100, and a new digital TV is under $400 (many are), any TV/VCR over about 5 years of age will get retired.  We have one digital capable TV, the VCR is analog and the second TV is analog.   I expect to replace the VCR with a PVR sometime in 2010 and the second TV in 2011. 

Seems though finding OTA based PVR's is very difficult, most retailers only have satellite or cable compatable ones, but that's another thread for another time.