Ok so my hunch based on just the trailer, Prior movies up to Thor, and this trailer.
Movie opens with Thanos Attacking Thors ship. He beats them down, throws thor and hulk into space. Kills a bunch of peope. Loki gives him the Tesseract and he crushes it for blue stone. He goes to NoWhere and takes the purple stone from thor 2 fro mthe collector and pulls in the guardians who find thor in space. He has two stones and heads to Earth. On earth Hulk lands in NY and meets up with Tony and Strange after falling into Stranges house. Thanos Invades Earth. Stark, Strange, Hulk, Spiderman defend NY and get help from Vision and Scarlet. Vision gets killed and Yellow stone taken. 3 down. Thanos Army invades Wakanda for the 4th stone, you are probably right that its there. Cap and Bucky are stil in Wakanda and others come to help defend the city. Meanwhile Guardians show up to earth with Thor to help.
The last two stones, one is with Strange and one is with Nova corps, so Unless the guardians bring that one to try to use it against Thanos, I dont see how that one fits into this movie. And We know Dr Strange is planned for future movies, so we can assume he makes it out alive, but will he lose his stone? I wouldnt be shocked to see Thanos end the movie with only 4 stones at best. Which confuses me since 4 is a separate movie now instead of part 2. Maybe he clears out Earth and heads for Nova corps planet, and movie ends with some of our heroes dead and leaving with the Guardians to fight Thanos in space.
Still seems kind of silly that in an entire Universe, Earth had the Tesseract just hidden here, the Aether hidden here, and the Time stone in a amulet on earth. So 3 of the 6 on a planet of normals.