AFAIK there won't be a new "NXT-G" -
but there surely will be a new grafical programming environment, just for beginners, again based on a new Labview version, targetting the new operating system and firmware, and it will also be downwards-compatible to the old NXT firmware.
As far as NXC already provides standard C-syntax there won't be much difference to real ANSI C, I personally don't worry about that, but if we got a real ANSI C compiler then we hopefully might have many additional standard C features on top. It will probably more concern the API functions than the syntax of basic C commands, but API functions can be simply #included by a header file.
NXC CHESS for NXT: http://www.mindstormsforum.de/viewtopic.php?f=70&t=6790
indispensable for NXC + EV3-C: easy + trouble-free network & sensor+motor remote control for rs485, BT, USB!