Your idea is a good one. I have that same combo and it's great, not only for video editing, but for all other work I do when in the office. I'd buy a current MBP, they are proven, stable, fast, and upgradeable.
The upcoming models are hyped like everything else new. I upgrade at each refresh cycle, and whether it's a new MBP or ThinkPad (I use both) they never live up to the hype. Oh sure, there are incremental speed and other small differences, but never the speed demon or battery stretcher they're made out to be.
Besides, if indeed there is a shocking increase in speed or some other feature set you like, selling the current model is very easy and will return excellent resale.
Good Luck 🙂