Marvel Studios has hinted that the First Family is indeed coming to the MCU at some point in the future, yet why not usher them in with a salute to the original team? It’s possible that, in their own dimension, the veteran team could also be looking into the theory of multiple dimensions, and they could actually end up stumbling upon the MCU.
When it comes to what takes them there, it could be anything from an interdimensional issue to a regular exploration mission. Afterwards, their visit would leave the heroes of the MCU wondering if such a team exists in their own world, leading to that eventual reveal later on. There are a multitude of ways to pull it off, but I do think it would be nice to revisit these characters and see where they are over a decade later. Plus, how cool would it be to see the MCU heroes react to Johnny Storm resembling Steve Rogers?