The most compelling "need" for 4K immediately is in the 3D Passive monitors market. Regardless of what you may hear from sales and marketing types, the truth is that technically, the passive monitors do reduce the resolution in 3D mode, so given a 4K panel, the reduction puts 3D back in the full HDTV resolution that we get with 2D.
The use of 4K for 3D sounds nice, but there is no need to jump into it for 2D content display since there are no present plans to distribute 2D 4K content. You are correct to assume that when you wish to display 2D 4K content, it won't just be the monitor or projector, but the entire signal path and source content will need to be 4K compatible.
My only reason to want 4K is for 3D passive.
So, will it be doomed? I doubt it. It will continue to develop and as the cost of these 4K sets come down, other parts of the display chain will surface, including content.
To compare where we are with 4K is to make a comparison in 3D to where home 3D was back when the interleave alternate line systems came out for CRT TV's. About 20 special titles were released before it faded into the background. Then the only long term 3D format was anaglyph which never did die off. Then active shutter system broke and 3D has been alive as a specialty viewing format for several years now.
Presently, the 4K $20,000 panels are there for those who just have to have it and have the money. I assume none of these buyers even have any way to generate a 4K signal for display. The time to get into 4K for 2D content is when you see the entire display chain being offered, ie, movies, network channels, players, new bluRay disk standards, and switching systems in receivers that permit passage of 4K content. These panels are the horses that will pull the cart of all the other stuff into the market. We had the same leader in 3D. Unlike audio where we had content in multichannel surround long before the rest of the chain was out.