Originally Posted by psylockolussus
Because FOX is also developing spin-off films like X-Force and its already been reported the Fantastic Four shares the same universe with the X-Men. If the Fantastic Four will share universe with the X-Men, it would be weird if the FF are set in the 2010s while the X-Men are stuck in the 80s. Are they gonna do a X-Force film set in the 70s or 80s or 90s? And if a cross-over happens, they will have to use time-travel once again.
What difference does it matter WHEN/WHERE the story takes place? As long as they introduce new things then they are expanding. Regardless of what they do with X-Force & F4 it wont change the fact that FC led X-Men movies set in past decades are a perfectly viable option for expanding the universe with new characters/stories.