I wouldn't think the screen would get outdated like the other hardware does in a media room setup. The only thing that "could" change would be going from a 1.78 (16:9) ratio screen to a 2.35 (21:9) ratio. I am going through this thought process now. I had a 1.78 screen at my old house and am thinking of going with a 2.35 screen in new one. Essentially the 2.35 will allow you to get rid of the black bars seen on cinemascope movies, but this requires "zooming" of projector, video processing and/or an anamorphic lens (very expensive).

I have been using Display Wars to figure out what size of 2.35 screen equates to a 16:9 screen. Right now I am leaning towards a 125" 2.35 which would equal a 99" 16:9 screen.

I hadn't thought about changing aspect ratios for the screen at some point. In that case it seems like it may be a better move to forgo a screen that mounts in the ceiling so you can have more flexibility down the line as opposed to having a built in that would take some effort to redo if you ever wanted to in the future.