My thoughts are that MPEG-4 will be around for a very long time. UHD will take awhile to get any sort of traction (I'm thinking 10-15 years). HDTV has been around in one form or another since the '80s, and is just within the last 3-4 years seeing widespread adoption. Heck, the Russians had a 1125 line analog system as early as 1958 for military applications!
http://en.wikipedia.org/wiki/Hdtv
Anyway, compression technology is constantly improving (look at x264 over the last year!!), though I have a hard time imagining what the next "big thing" will be. Available bandwidth and storage capacity continue to increase at astonishing rates (well... storage at least), which lessens the need for super awesome compression.
I imagine by the time we need to transmit / store UHD on any sort of scale, something new will be developed to fit these needs. I wonder if something intermediate, a-la 4K (RED camera, anyone?) will fill the void.
I'd like to see a trend towards quality - i.e. higher bit depth / wider color gamut. This mostly means better displays. Unfortunately, most people either don't care, or can't tell a difference (realistically the same thing).
Who knows... I'm pretty damned happy with BluRay for now... especially my half-size backup MKVs!
~MiSfit