Can you explain your reasoning on why do you think a new game is going to be announced for the 10th anniversary in 2021? Do you think kodaka will work on it, considering he left spike chunsoft for Tookyo games? (Unless the dark fantasy SC IS the new title... which is a possibility.)
My reasoning kind of boils down to: it would make sense to release a new game for the 10th anniversary.
DISCLAIMER: This is all just speculation, not fact.
As I've mentioned before, SpikeChun is a company, and not using a decently popular IP that's penetrated mainstream consciousness would be a puzzling business move, especially in light of all the effort they're doing to keep the series relevant via the 10th year celebration.
Second, if we were still on schedule and 2020 had not pulled out the stops on ridiculousness, it would be about 4ish years between V3 and hypothetical new game. That's a pretty decent chunk of time to develop a VN with some action elements, if previous DR dev cycles are any indication (though many of them tended to overlap, SDR2 was released 2 years after the first game, and according to a bajillion interviews I've read over the years, was not originally planned while they were working on DR1).
Third, @blackflirtlarping let me know that in an interview about Death Come True earlier this year, an interviewer said to Kodaka something about ending the DR series on his own terms with V3, to which Kodaka responded that he wouldn't be so quick to say DR is over.
As for why I think we haven't heard anything yet, well, if you aren't going to announce a new game at E3, or TGS, or GDC, or on the anniversary itself (which I suspect would be the original announcement date), it makes the most sense to announce it last. Fans who are hyped up for a new game announcement are at a fever pitch, and fans who assume this is a merch run only deal get a nice surprise. Plus this hypothetical game would presumably be affected by Covid circumstances, and might be behind schedule.
I dunno if Kodaka will be involved or not. I hope he isn't, personally, or his involvement is minimal, for two reasons: 1) he doesn't seem to want to make DR anymore, and 2) I'm dying for a different perspective.
Finally, a new DR game may not be the exact same formula we're used to. There are plenty of ways to have death game narratives besides the murder-solving six act structure, though again, business wisdom would probably be to avoid shaking too much up. Maybe it's an offshoot series or something, like how Persona is a SMT spinoff.
I could be way off of course, and we're building up to two hand towels, but this is what makes sense to me.
Here's some things I think are probable events we'll see in 2021:
DR:AE inspired laser tag style event (we had one of these in...2014, I wanna say?)