I hope Grant has a cameo in the film since it’s only right.
He fit more with the Legends than he did with Team Flash. Plus, I like that he had elements of Young Justice Wally in him, with him holding onto a 'souvenir.'
Although Wally's character blended well with the Legends, the problem is that he's too powerful to be on the show as a fixed member. Wally could easily solve most of their problems with his powers.
Grant Gustin it seems has agree to a 9th season with 15 episodes.
‘The Flash’: Grant Gustin Nears New Deal, Paving Way Season 9 Renewal – Deadline