So even though it’s unlikely Jon Watts will direct a fourth Spider-Man movie, perhaps the fact that he’s directing the Fantastic Four reboot means that Spidey could show up in that feature.
After all, Spider-Man and the Fantastic Four are closely connected in the comics, and the former could easily be used as an anchor of sorts to help audiences become familiar/reacquainted with the latter.
Finally, if you’ll indulge me in some speculation, back when Marvel Studios and Sony worked out a new arrangement for Tom Holland’s Spider-Man, it was announced that in addition to Spider-Man 3, this version of the Wall-Crawler would appear in a separate Marvel Studios movie.