it's nice, but too bland, can make a good avatar though !
a few tips:
- if you add his sharingan it will give some much needed colour to it...
- you can also throw in a full-coloured naruto logo on the top-left hair area, it will help some too... you can get the naruto font and write in sasuke :-) that will be cool ...
- line stroking is a must in such a portrait, especially when cell shading...
- add a boarder, and a good one -> not just a black rectangle but something ornamental that fits sasuke like a snake or an eagle or some play on the Uchiha's symbol...
the point is that their's a million things you can do with it that will add some interest to it without changing it too much or working too hard...
hope this helps... cause I really like your colouring and stuff...
I personally haven't read the chapter or the spoilers so I'll be waiting for the raw to decide, but having sasuke in the incoming chapter sure is good news, even if it only end's up being some flashback...