Trailer looks good. I'm team #recasttchalla but I'll wait just like the other MCU movies that came before to reserve judgment. Marvel knows how to make a good trailer. Their recent trailers have overhyped or set false expectations lately unfortunately.
Not my idea, but I think the only way I'll be cool with not recasting T'Challa is if Doom is responsible for killing T'Challa. There's no more badass way to have him enter the MCU than having him responsible for his death. I think this is highly unlikely, but would give great gravity to his character especially as I am hearing he is the driving force behind Wakanda and Atlantis going to war in this movie.