The involvement of Cannonball is not new information, with him having long been one of the reported members of the team in New Mutants. Should this report stay true, Cannoball will be joined by Wolfsbane, Magik, Mirage, and Sunspot. There have so far not been any official casting announcements for New Mutants, but Maisie Williams for Wolfsbane and Anya Taylor Joy for Magik has previously been rumored.
With production reportedly starting early next year, casting announcements should be on the horizon. Given the lack of contrary reports for actors in the running for Wolfsbane, Magik, and Cannonball, it seems likely at this point that all three of the previously reported actors will get their respective roles. If they are, they should be joined by James McAvoy’s Charles Xavier in New Mutants, unless his contract has not been extended.
Plot details for New Mutants continue to be secretive, but now that multiple drafts of teh script have been completed, Fox and Boone should have a very clear idea of what the story is going to be. How the New Mutants team plays into the rest of the X-verse remains to be seen, but the project appears to be in good shape at the moment, especially if Wolff signs on.