I can't see 1080i being important to the PS3, atleast in europe (UK).
Many of the current plasma TVs only support 480p.
I bet a very large number of the PS2s in the world are in peoples bedrooms, even if they do have HDTV it will be in the living room, it's not where the PS2 is and i can't see this changing drastically for PS3. Cause girlfriends/ wives will still want to watch Corrie/ Eastenders in the living room while we're playing on the PS3
Most people I know have 28-32" CRT's (£300-£800), many have just bought them and have NO intension of upgrading in the life-time of PS3.
I've had my 36" Tosh (with no pro Scan) for nearly 4 years and have no plans to upgrade in the lifetime of the PS3.
Most people are NOT going to bother spening £s on a new TV when the old one is fine JUST for PS3. People have more important things to spend money on like mortgages, cars, going out, holidays etc...
I know plenty of people with PS2s and X boxes who haven't even got widescreen TVs, and some are still using portables, still fine for PES
Then when you consider all the kids which will have PS3s bought for Christmas and birthday presents, your average kid does not have a HDTV in his bedroom.