That's what people were saying about 1080p when the PS3 came out too.
No content, too expensive, consumers won't care, won't matter unless you have a huge screen.
But now, they're putting 1080p in phones.
I'm not saying 4k will displace 1080p but I wouldn't rule it out completely either.
That said, I'd wait a couple of years to see if there is content released in 4k. Second or third gen displays are likely to be much better as well as cheaper. Maybe also a display tech other than plasma or LCD may make an appearance.
1080p isn't the same as Bluray. One is a disc format (hard to push), the other us a spec on a TV, computer, or phone. You just get it over time. Bluray worked because DVDs on large Tavs looked terrible.