This is one reason I'm passing up Blu-Ray and HD-DVD. Blu-Ray's fine if you've got a PS3, and yes, these movies do look better on 1080p TVs...but you're kidding yourself if you think 1080p will be the best TV resolution in 2 or 3 years.
Then we'll get "enhanced Blu-Rays" or "Blu-Ray 2.0" for the 2000p TVs or a resolution like that...and all the 1080p Blu-Rays won't be as good as they could be.
While I agree it will get better, I think it will be a lot longer than 2-3 years before there is any serious increase in size. Broadcast TV generally does not have the bandwidth at the moment to even do 1080p and a large number of consumers still consider standard definition 'good enough'. Even if an improved medium comes along to deliver it, a lot of people who are interested in this type of stuff will have already upgraded and will not be ready to upgrade again so soon.
And really, will anything larger really be that much better? At 2160p, for a 60" screen, you need to be sitting about 1m away to get the "full benifit" of it. Are people really going to notice a major difference between 1080p and 2160p at comfortable sitting distances?