But even then most DSLRs are at least 20MP+ giving enough wiggle room to crop/manipulate the image and still have a high enough resolution to display on 4K devices.
I don't think it will be an issue for a good while yet and by that time I'm sure new bodies will come out to take advantage of it.
I think the parent was talking about currently available models. The D90 quoted is from 2008, and nowadays even good compact/superzoom cameras can do useful 4k photos.
