Tweet makes me wonder if the BP2 is going to take place after the snap when T'Challa is presumed dead. That way the film would be structured as a mourning of T'Challa in universe and the meta commentary would be about the mourning of Chadwick. Then plot wise they could tell the story of what happened in Wakanda during the 5 years where they had no Black Panther.
Then in a future film, like BP3 where Coogler may not be involved, it could take place after end game and possibly feature a recasted T'Challa.
It's a thought, though the counter is that Shuri was also gone after the snap, so the story would basically just consist of Okoye, Nakia, and M'Baku, in world we already know gets reversed, and that probably wouldn't be a worthy enough follow up to one of the biggest blockbusters of all time.
Thinking about this further, they never actually showed Shuri die. If I recall correctly, the only evidence we had on screen that she died was a video screen showing her "missing" along with the other snapped victims. Sure she came back through the portal with T'Challa, but not everyone that came through that portal was dead, see Okoye.
So I guess it's possible that they can retcon Shuri's story in the five year gap between Infinity War and End Game, and write that she went underground/off the grid to do black ops shyt with Nakia or whatever, but was around doing shyt, and wasn't a victim of the snap.
Until we hear otherwise, I think it's possible that BP 2 is set during the five year gap before T'Challa returns.