If Apple releases a Macbook Air with a faster CPU/GPU + Retina display, I'd sell my MBP immediately and get it.
Are we talking about the non-touchbar "Pro" here?
If I needed a Mac laptop for office, communications and light web/script development on the move I'd seriously consider the
current Air rather than the nTB MBP. The only clear advantage of the nTB is the retina screen - in most other respects the Air is simply a more practical design
for this class of laptop: Yup, if I'm buying an ultraportable laptop with a low-power CPU/GPU then I'm not going to worry less about 40Gbps Thunderbolt 3 or connecting the only 5k display on the market and more about whether its going to work with my existing stuff or if I'll need a dongle when someone passes me a memory stick... Having a decent keyboard and a sensible-sized trackpad also trumps any GPU/CPU speedup that you'd need to run benchmarks to notice.
The only sticking point is the Air's screen (which, frankly, I can live with, and the MBA docks nicely with the LED cinema display on my work desk - the MBP would need multiple dongles and a new power supply).
If Apple updated the Air with a retina display and newer CPU then it would be a no-brainer.
...as for the more powerful MBPs... In the past, I've used an MBP as a main machine. The new MBPs were so ~meh, though, that I've now got an iMac on my desk to handle the heavy lifting (far more bangs-per-buck than any new MBP) and would certainly consider a new (non-mucked-up) Air for my portable needs once my old MBP expires.
Unfortunately, I'm sure Apple will find other ways to "improve" the Air - probably removing all the useful port, adding their magical new butterfly keyboard and over-large trackpad while shrinking the battery for the sake of shaving a few mm off the thickness) or it would kill the nTB MBP stone dead.