Shuri may have also been killed by Thanos’ snap according to the newly released and dealing with the aftermath of the Decimation given. Considering that Endgame might have the heroes rely a bit more on science – both Stark’s Binarily Augmented Retro-Framing (B.A.R.F.) and the Quantum Realm are expected to be important – Earth’s Mightiest Heroes could certainly use Shuri’s genius, either to help crack time travel or bring back Vision.
The question remains about Shuri’s possible whereabouts. Marvel Studios was very careful in deciding what to show fans in the Avengers: Endgame’s first trailer and based on what we’ve seen, everything that has been revealed takes place early on in the movie so as to not to give anything away plot-wise that fans don’t know already. Similar to what they did in Infinity War, it’s safe to assume that the Russos, alongside writers Stephen Markus and Christopher McFeely, have planned more than a couple of plot twists. One of them could be the reveal of where the princess of Wakanda really is.