So having just finished the new What If! Flash Thompson Was Spider-Man issue that came out yesterday, I've got to say, I'm going to be very disappointed if this alternate version of Flash doesn't show up at some point in Spider-geddon. This version of Flash is simply too good of a character for him not to show up again at some point, such as Spider-geddon.
Also on a side note, since I've brought up the What If comics, I'd really hope we get to see the Peter Parker from 1980's What If! #24 "What If Gwen Stacy Had Lived?" show up and learn how the rest of the events of his life transpired. I mean, it's been 38 years since the issue and it would be kind of nice to finally see some kind of resolution to that interesting cliffhanger from the end of that issue, where Peter's wedding with Gwen tragically ends with his public identity by Jameson (who himself learned after the Green Goblin leaked the information to him) being revealed and exposed to the world, resulting in Peter having to go underground with the police hunting him. It's always annoyed me that we never saw some kind of a resolution to that during the events of Spiderverse.