this is a complex question, even though it doesn't seem like one
no one knows for sure when new mbp's will come out... there's some speculation about sometime this month, but that is only speculation. add to that, no one knows what the new mbp's will have inside/look like, they can only go by what intel's latest offerings are and then speculate how apple will configure them.
the reliability of the gpu used in the current mbp's (as well as the majority of higher-end notebooks from all manufacturers) is in question right now based on some stuff going on with the materials used in these chips...lots of info on these boards about this.
the general theory around whether to wait or not is based on how difficult it is for you to wait. given the noise about sept 9 or 16, i'd say wait till then if at all possible. if you do go with the current gen mbp, the whole gpu issue is something you'll need to decide whether you're comfortable gambling on (i.e. may or may not be an issue, apple/nvidia may or may not deal with it, even if it is an issue it may or may not affect you during the life of your mbp)...
my local apple stores always tell me that if an upgraded/new model of whatever i'm buying, is released within the 14 day return period, they'd let me exchange without a restocking fee.
mjb