If RED's claims are you can get 4K content at only 2.5MB, then it's simply a matter of content being available...and you buying their gear. 
 
In all honesty...any "HD" streaming today generally sucks, so from my perspective, and those that actually want a decent picture, no one will want it if it's as crappy as today's content.
		
		
	 
I'm interested to see who wins...RED said they have a 4K player and distribution system coming, but Sony also just make their own 4K distribution annoucement.  So hopefully this doesn't turn into the Betamax/VHS or HD-DVD/Bluray deal again with digital format wars.  RED seems to be king of 4K, but they 
still haven't released their 4K laser projector or 4K REDRAY distributed player, and Sony has a pretty good track record of actually coming out (not saying that RED is vaporware, just that they don't really commit to dates, so it's hard to pinpoint any kind of schedule).
I like stuff like HD Netflix streaming and VUDU better than actual Blu-ray discs.  I've had a really bad experience with Blu-ray discs...problems playing discs, having to download updates over the Internet, waiting for the menu system & advertisements, just a really slow & lame experience all around...now I just say screw it and rent it on VUDU and it looks great!  Or stream Netflix HDX or whatever.  If they can really do the 2.5 MB/s thing, that would be really cool, but they'll also have to coordinate not only with movie studios, but also with iTunes, Amazon, Netflix, etc. if they really want to pull in all of the content.  It will be interesting to see how all that plays out...I'd really like to see just a single box, and then you choose your vendor within that box (like a PC...you choose the software).
Film is still a higher resolution than almost every digital camera out there.  A 70mm IMAX film is roughly equivalent to 8K (I think about 10K equivalent, but even old films like the Wizard of Oz are being scanned in at 8K since we have those scanners available), so we still have a ways to go before we burn out the old movie resolution.  I think Jim at RED said that 35mm film is roughly equivalent to 3.2K, so a bit less than 4K UltraHD.  A lot of modern movies have been mastered in 2K and I'm sure we'll be seeing more go into the 4K workflow ($$$!).  Panavision just announced a 
70mm-equivalent digital camera (the assumption is that this will be an 8K camera), so I think we'll start seeing a lot of 4K content in pretty short order, as long as a distribution system is available - either by disc, download, or streaming.