Now would be the time for iTunes movies to come in 2560x1080p then, and a new

TV to go with the Philips 21:9 cinema.
Since almost zero percent of millions of movies made are finished in 4k, this would be like wishing that iTunes music would be 24bit/192kHz apple lossless codec, when most of the masters are 16bit/44.1kHz.
Once again this is video market share:
https://forums.macrumors.com/showthread.php?p=10556879&#post10556879
Even if Apple would have 100% market share of both online & mobile video in 2013 US, that would be only about 15% of overall market and nowhere near for Apple to establish a new video format.
Hdtv formats were standardized in 1998 and Apple is still not offering even 1080 lines of resolution in its distribution in 2010. Blu-ray has offered that from 2005 and will hold 4x market share in 2013 than online & mobile combined. Again global market has even bigger difference.
If there's a new format established it will be BD2. I guess it will come somewhere around 2013. Key factors in enhanced quality should not be vertical resolution, but it might be easiest to advertise.
1080 is quite enough for active picture height, if widescreen movies could have it. In square pixels 2.40:1 AR should have width of 2560 pixels. More important issues would be better chroma resolution and bit depth. When displays have much better contrast than before, 8 bits per color isn't enough for smooth gradients.
Anyway there might be 1440p or 2160p or WHATEVERp (= content maker can choose the resolution and players have mandatory scaling), but sure thing is that this new format will need to be introduced by market leader (=br) to be succesfully adopted.
Btw, that philips telly is pretty remarkable piece of engineering; it can't take in the native resolution of it's panel...