I suspect that it will be a bit of both:
- price slightly increased for new MBair and MBPro.
- price slightly decreased for MB.
This will help to differentiate them more from each other, and I suspect that the MB will be priced so that it will be clear that it is intended to be the entry-level portable Mac.
In the end, this is all just guesswork, and nothing that Apple does will end up surprising me.
Meanwhile, you can still get the 2015 hardware for cheaper if you look around, and perhaps even the 2016 stuff. For example, Best Buy where I am has some of the 2015 MB's in stock (1.3GHz model, with 512GB) for $100 off right now, bringing it down to $1599 CDN. If I were not wanting the 2016 model, then I'd get it. I'm waiting for the price to stabilize though, and since I'm still using my mid2012 MBP (with aftermarket SSD and 16GB) I have zero "need" to replace it with a MB right now. So, I can wait.