The people handling marketing and products at Blizzard, and EA, and Bethesda aren't in touch with their most loyal fans. I can only imagine how much money there must be in in-game transactions, given that all three companies continue to upset fans that don't mind paying $60 for a new release.
Instead of saying "don't you have phones?" they should have said "We are working on a new Diablo PC title but we aren't ready to talk about it yet".
Would have been a very different reaction.
The only "better" answer that I can think of would be a vague, general hint that Blozzard is working on more titles than those that are announced. But that would immediately be interpreted as "Diablo IV confirmed" and blown out of proportion.
The gaming community has in recent years developed a culture of latching on to smallest of hints, letting their imagination roam freely to create a kind of groupthink dream of what the project would be. And than they react not only with disappointment, but also with hate, anger and aggression against the developers when these dream bubbles are busted. This lack of moderation in the community is disconcerting and if we don't find efficient ways to dampen that, we will see this get out of hands.
Games are made by companies for profit. If they release something that you like, enjoy it. If you don't like it, move on. I don't understand any need to fuel hate to the levels we are seeing repeatedly these days.
I know, that's why you usually prepare a series of answers for QAs.
And sure, some things you can't prepare for, but a PC question from fans of a PC game is inevitable.
I'm almost certain it was partially rehearsed.