I'm sure that they'll be looking to see how Spiderman: Homecoming does, now that he's in the MU (but Sony keeps the revenue he creates).
May 3, 2002
Spider-Man $821,706,375
Jun 30, 2004
Spider-Man 2 $783,705,001
May 4, 2007
Spider-Man 3 $890,875,303
Jul 3, 2012
The Amazing Spider-Man $757,890,267
May 2, 2014
The Amazing Spider-Man 2 $708,996,336
The only movie that bucked the downward trend was Spiderman 3, but that movie cost 140m more than SM1 and 60 more than SM2. Xmen has also followed this downward trend (at least before DoFP, I haven't seen the numbers since).
I don't think that Fox wants to sit there with FF on the shelf, when you have properties like Ant Man and Dr Strange making money hand over fist. Fox is losing billions on FF, and they are going to have to produce another movie before 2019, or Marvel gets the rights back anyway. Relations might be frosty, but money usually overcomes stuff like that.