The goal is for the long awaited predecessor to be the superior game, that’s just how Diablo games have worked. Other games you’ll have sequels having xxx quality better but not xyz thing that made previous title great so you’ll get to swap tastes between the two.
Not Diablo though, let’s be real the only reason D2 is appealing is because D3 failed the loot system and to make it appealing you have to fix it every season with something new. So if D4’s “army of developers” starts having the superior loot system as it’s looking so far with a superior combat and skill system there will be no need to continue with D3.
Worst case scenario, the combat system isn’t as fluid as D3 (it’s highest good point) , but everything else is superior…I’ll still deal with the lagging combat system and invest all the time because likely they’ll improve it over time but that might make me blast a season for 2 weeks in D3 till then.