That is what we hope, remember D3 for many who bought it at start based on Diablo name was already no ARPG according to many who left D2 after the 1.09 patch and basically developed for another player base, even most who still played D2 1.14 online thought it went to far off the ARPG path for their liking.
With all the new mobile players that D:I brings to the franchise it is quite unlikely Blizz will not try to retain at least part of these and that will impact design of D4, both at start and likely even worse later if D4 does not appeal to those new fans.
Branching out a franchise, tends to make it less and less fun for their old core fans, while trying to hold them will displease the fans that liked that p2w monstrosity. There is no pleasing everyone and if do you will displease most besides the few that like their game as it turns out.