I wouldn't be too worried about the M3 becoming a pure GT car. The E46 M3 was never a good GT car (it's not comfortable enough for long drives), but it was an awesome performance/sports car for the track that you can drive on the road.
Many people are concerned about the "purist" approach, and what that means to most people is a stick shift manual transmission, RWD, minimal electronic aids, and minimal weight. For most people, cars like the Lotus Elise is the "purest" you can get these days. If that's what you're looking for, the M3 is not for you. Let the M2 or whatever lower end model BMW M is making take on that market. The standard M3 has to beat the top of the line C-AMG car, top of the line RS4, and top of the line IS-F, which are not bare bones cars.
I have no doubt the new M3 will totally eclipse the performance of the E46 M3 and will be much more "hardcore" than its main competition (C63 AMG, RS4, and IS-F). It may or may not be as fast as the E60 M5 in a straight line, but it will definitely handle a lot better. If what people are saying are true, then the next M3 will have performance that will match or beat the Porsche 911, which is all time greatest sports car ever made, IMO.
Just like the E46 M3 outperformed the E39 M5 on a track, the E92 M3 may very well outperform the E60 M5 in the same way.