One thing we know is that Marvel are very good at playing the long game. Iron Man with a Nick Fury cameo, the hammer of Thor abandoned in the desert, Stark with Thunderbolt Ross in a bar. Small teases, little glimpses, passing mentions.
Since Disney paid over $70b for Fox, this reacquired a number of valuable properties for Marvel Studios to play with. Chief among them are Fantastic Four and X-Men. We know the MCU isn’t going anywhere yet, so you just know these characters will arrive in the shared universe sooner or later.
Now it seems the long game may be afoot again with the first glimpses of X-Men iconography appearing in the MCU. A set photo for The Falcon And The Winter Soldier has shown some imagery that appears to be the flag of Madripoor.
This is a famous location from the X-Men comic books. It is a southeast Asian island that is a safe zone for criminals under the control of Madame Hydra / Viper. Wolverine once lived there under a cover name. Here is a clearer look at Madripoor’s flag.
So while Marvel Studios and Kevin Feige are very clear that there is no X-Men or Fantastic Four in this phase of the MCU it is clear the breadcrumbs are already being laid.