We don't even know for sure that there will be a new refreshed one anytime soon. Its about time, the appropriate processors should be available around now, but nobody outside of Apple knows what the plan is. Also, when it comes, we don't know if it will be a quiet bump of the current models to the latest processors or a major re-design along the lines of the MacBook + a switch to USB-C/TB3 ports.
A rMB-style design with 2 USB-C/TB3 ports and nothing else, replacing both the 13" rMBP and the 13" MacBook Air seems likely to me (it won't go down well on this forum - but unless the design team at Apple have been replaced by alien pod people in the last few months I'm sure that's the way they would go).
Best advice is as per the post above: if your old Mac is giving you problems, buy now, otherwise wait.