it's not unusual that the next model will have a different size. Yamaha users, exchanging the PSR 9000 by Tyros can't use the old case, the same as Korg users.
About gig bags, no problem. The same gig bag fits with Yamaha 9000 pro, G 1000, VA 76 and G 70.
Possibly the customers will understand the G 70 as a better "V-Combo" and use it in a band.
If I had the money, I would combine G70 with Yamaha Tyros and the G70 styles use only, when I don't find a satisfying Yamaha style (because there are many Yamaha 4 variation styles available and no Roland 4 variation styles).