Im gonna be honest. I think 4k is a little hyped. I've seen it, used it... and was less than impressed, especially comparing to a 2k resolution like 1440p or 1600p. Especially on a monitor. The size of average monitors just isn't sufficient to notice the pixel density difference. Sure, you'll see less jaggies in games and the image may appear a little sharper, but im not lying when I say my HPzr30w 2560x1600 monitor hurts my eyes a bit. Aside from less jaggies at 1080p, the only real difference I noticed switching to it was smaller, harder to read icons, a little more desktop space, and better color vibrance (though that's from the S-IPS panel and chipset, not so much the resolution).
In fact, Im assuming most are going to buy a 4k monitor, and feel less than impressed if they're coming off a 2k resolution. They may even feel a bit stung coming off a really good 1680x1050 or 1920x1080 monitor with some great hardware chipset in it and ppi. It's because simply at desktop or workstation monitor sizes, its just not a significantly noticeable difference. They'll simply buy it because its the new thing to have.
And don't even get me started on TV's in 4k. Unless your doing 70 inches or greater on your shiny new 4k TV, its gonna be hard to distinguish from 1080p at those viewing distances and sizes, especially with some really good 1080p chips and pixel density in some of the higher end ones.
Same kind of rules apply for your average monitor sizes... sure, your closer to it than a TV per se, but your still a couple or few feet away on an already small screen. The difference isn't nearly as mind blowing as you see on say, a 80+ plus 4k tv were the pixels can hold the image together very well at larger panel sizes. After all, that's what it was designed for... to keep pixelization from appearing on larger screen sizes. And by that I mean TV's in excess of 70 inches, where the compaction of pixel density starts to show beyond at 1080p,
Honestly if you currently have a 1080p, and want to save some cash, jump to 1600p first while your waiting for 4k to come down in price. You'll likely notice little difference and have saved quite a bit in the process doing so especially if going with standard monitor sizes. Also, if you hop onto 2k monitor right now, youll have no worry of AA eating up your VRAM, youll still need less of it than 1080p, and itll make 4k even harder to distinguish from using it to clear up jaggies.