Last I heard, Apple doesn't make monitors so they aint innovating anything, Whoever builds their panel (LG, SAMSUNG, AU OPTRONICS, etc) are the innovators.
While it's true that Apple does not manufacture their own panels, this doesn't mean that they are not a driving force for innovation. Apple was first to market with a high-DPI smartphone (the iPhone 4), first to market with a high-DPI tablet (the iPad 3), and first to market with a high-DPI laptop (rMBP). Do you think that's a coincidence? No: Apple has used its marketing power specifically to push the supply chain to create affordable high-DPI displays. This has been to the benefit of all users, including those of us who use Android and Windows. If Apple hadn't shown the world how much better a high-DPI display looks, people would have puttered along at 100 DPI for years and not known what they were missing.
Affordable 4K monitors have been around for PC for over a year so Apple is actually behind in the ultra HD monitor space.
Actually, I'm still waiting for a suitable 4K monitor. Currently you have a choice between a bunch of 27" 4K monitors using the same mediocre TN panel (no thanks) and a couple of 32" 4K monitors using the Sharp IGZO panel, costing over $2000, and supporting 4K@60Hz input only via the buggy MST hack (again, no thanks). Then there's the Seiki TV, which is dirt-cheap and has a nice 39" VA panel, but is crippled by a 30Hz refresh rate.
Unless a good IPS or VA 4K monitor comes down to below $1500 (preferably below $1000), the Retina iMac looks like a better deal.
Having said all that, If I were to buy a 5K display I kind of would like for it to be a little bigger then 27". I'm thinking more like 32" to 40". I already have two 4K displays (28" and a 39") and I really like them. 4K and up can really benefit from having larger displays IMO which helps negate the need for scaling.
My dream display would be 39" with an 8K resolution (7680x4320) and 120Hz refresh rate. High DPI, tons of screen real estate, and fast refresh all in one package. That won't happen for many years, though.
Now that I think about it, if Apple is committed to 5K then every new piece of new hardware from them running OS X should have adequate support to push a 5K external display such as the upcoming Dell which supposedly needs dual DisplayPort 1.2. It doesn't really matter how hackneyed or patched together the connection interface may be it still needs to be supported.
No off-the-shelf video card supports 5K output over a single-tile connection. It has to treat the output as dual 2560x2880 displays. Many first-generation 4K monitors work this same way (even though DP 1.2 can handle 4K@60Hz, the older scaler chips can't), and this causes all kinds of problems: failure to wake up after sleep, only one half of the screen showing up, and so forth. I don't think Apple wants that kind of experience for their users.
On the other hand, maybe since Apple controls the whole OS, they won't have these problems as severe as on Windows. They have a lot more ability to lean on AMD for better driver support than the average consumer does, and more ability to get their issues prioritized - especially since Apple is probably AMD's third biggest customer now, after MS and Sony.