DMC2's placement in the series timeline was set in the far future during the promotion for DMC4. This was the series canon until a few months ago.Did he? I can't remember Itsuno himself ever stating DMC2 was far off in the future. Even then, it would have been something said a long time ago. Him saying heaven not existing was something he said in an interview done by Capcom themselves when promoting DMC4SE. At any rate it was never a terribly important detail. Heaven existing however would be a massive paradigm shift, and a way bigger development than anything DMC2-related.
A lot of people assumed that heaven is a thing in the DMC universe until Itsuno said otherwise.
That's the thing, though. Expect from Heaven. They expect it because they're thinking in terms of a Judeo-Christian framework. Remove that and it stops being "heaven" and instead something abstract and demon.
As for demonic angels, Bayonetta already does something like that.
The "Demon World" of DMC is also known as the Hell, the Underworld, Netherworld, and, Dark World, and Demon Kingdom, but is an apparent yet distinct allegory for Judeo-Christian Hell, and a 'Divine World' could be a distinct yet apparent allegory for a polar opposite. There are already Divinity Statues and Holy Water in this series, so I think expanding upon the nature of those particular elements would be a boon for the series.
An unprecedented imbalance of power in the 'Divine World' could be whipped up by any plot author to explain its emergence in the series, and should truly have no bearing or even tonal shift on the game.