I have a mid-2011 MBA 13" and looking to upgrade to an rMBP 13" as soon as a new one is released.
I agree with some others that if there is a redesign of the Pro series we will have to wait for an event such as WWDC but a simple internal refresh could come at any time.
While it would be great to get a new design, I do hope there is not too radical a restructuring of their macbook lineup as it may mean there is nothing quite right for me. I would be happy with something very much like the current rMBP 13" just with Skylake- a stylish new chassis would be a bonus. But if they drop 13" (going for 12 and 14 say), or strip away all ports like the MB, that may be bad for me.