Try Futile:
https://github.com/MattRix/FutileDoesn't seem to differ much from NGUI in terms of the core technique they use to render things, so it seems completely possible to free NGUI of this limitation someday.
Check it out -- very cool engine. I'm finding that NGUI really isn't suited for 2D games due to UpdateTransforms, which is unfortunate because it is always nicer to use a single library.
With Futile, I can get 15,000 2D objects (60,000 verts) on the screen all at once, all animating at the same time. Not that you'd need that many objects in a single game view, but point is, it's fast -- just not as convenient for simple UI. (Forgot to mention this is on an iPhone 4s)