The chassis is improving
Cat may create a new chassis, but I doubt it until 2017. The current platform works well (not perfect, but what sled is?) Refinements may include weight loss & perhaps different skis. Speaking of weight, there is a point where chassis reinforcement is required (I had an 08 XP and now have a ProRMK - light doesn't mean tough) But from a manufacturing standpoint, it simply isn't feasible to build different chassis for different engines, and certainly not for a mountain specific market (this is a reality). It is true that the 2012's had a bunch of teething problems, and Cat was very slow in resolving them (some were not resolved at all, either), but the 2013's and up have had significant improvements every year. For every person griping about the PC, there is likely 4 other owners without any major issues. The same can be said amongst the other manufacturers, Polaris and Ski-Doo included. If you read all of the forums and took it all to heart, and ignored all of the marketing ploys and "expert testimonials", none of us would buy a new snowmobile, although the fact is the new machines will take us places we only dreamed about ten years ago - if you don't buy into that go buy a 2004 REV, Edge, RX1 or 1M and ride it for a season.
Now, I'm not saying that the manufacturers couldn't build a better sled, but at what cost? Parts manufacturing is farmed out, assembly is provided by relatively low cost labour, it's simply amazing these things work as well as they do. But if you have to have the "perfect sled", go get one custom built - it will be light, handle great, have lots of power and fit and finish second to none - but it will not meet current EPA guidelines and will cost you a fortune to purchase and maintain.
It's always nice to have a "wish list", but be careful what you wish for