Tony is alone in the tower, the Rogues hiding in Wakanda. A portal opens (in the tower? in Central Park? I'm no longer sure.) and the Avengers sans Iron Man step through. They look different enough to make it obvious they aren't the team Tony knows (Steve taller and more muscular for instance) and they aren't hostile to him at all. They're the last living members of a world their Thanos has destroyed, Tony and/or Reed staying behind to control the machine that opened the portal. This new team is rallying around Tony to help him defeat Thanos. The Rogues call from Wakanda to warn Tony that they aren't who they appear to be, like Tony's too stupid to tell and revel in a team that won't turn on him. I think Rogers and Co. come to the tower and Iron Man's new team protect him from the traitors.
These are the parts I remember. Hopefully I got the details mostly right. Thanks for any help finding the story, or any one similar.