Probably not. Development has been more quiet since Windward is releasing on Steam and all, so there hasn't been many fixes lately. I believe the pro repo is slightly a head with a few things, but nothing major.
Question is if there will be any major overhauls or new features, but that mostly depend on time investment vs benefit as usual. If something is possible to do in NGUI but not in UnityGUI for instance, it might be a driver for more users of NGUI.
Some issues I could see being worked on in the future, or are a hassle to me every once in a while:
* Performance in very large scroll lists
* Blinking when switching screens (frame delay on activation)
* Interaction with 3d /particle systems
* Rework how labels calculate sizes so we can add [ size=14 ] smalltext [ /size ] without everything breaking.
Those are just from my own perspective - whether arenmook will work on them or not, is entirely up to him. It might be helpful to see what kinds of things people think NGUI lacks at this point, where they've had to modify core things to do it themselves, or buy other addons to it. Some things could just be built-in, I guess.
TL;DR: Probably not the last version, no.