One additional reason we might not see an updated MBP this year is the Infinity display. Dell has stated that it licensed the technology from Sharp, and that it has an exclusivity deal. The question is how long that deal runs, different sources say either August 2015 or December 2015. Either way, Apple might be interested in the technology, as it is getting excellent reviews especially in color reproduction, brightness and contrast. Apple has just switched to Sharp for the iPad Pro display.
So maybe Apples redesign plans include this display technology, and they have to wait for the exclusivity deal to end.
At least I hope so, as a redesigned rMBP with smaller bezels, smaller footprint and 100% Adobe RGB would be awesome.