If Fantastic Four: First Steps takes place in the 1960s how will they be in Avengers: Doomsday if that movie takes place in today's time?

I have been curious about something since the Fantastic Four: First Steps panel at SDCC. The director shared that the movie will take place in the 1960s. Also during the panel, Feige shared that the Fantastic Four will be part of both upcoming Avengers movies.

If Fantastic Four: First Steps takes place in the 1960s how will the characters be a part of Avengers: Doomsday? I guess I assumed that Avengers: Doomsday would be taking place in today's time. Will this movie also have a time travel component like Avengers: Endgame? And they bring the Fantastic Four from their time?

Did anyone else notice this? Wondering what other people think.