According to Slash Film, the rumor isn't true, and Scott Derrrickson is sticking with Marvel Studios.
I have it on very good authority that’s not the case. Never say never, of course, but he’s concentrating on the Marvel film.
Currently, it's only known that Godzilla director Gareth Edwards and Fantastic Four director Josh Trank are directing the Star Wars spinoffs.
Scott Derrickson is known for directing the Sinister films as well as a batch of other horror movies. It's speculated that the Doctor Strange movie may be going the same route and will be a supernatural horror Marvel film. It's also been stated that Joaquin Phoenix is close to signing for the role of Stephen Strange.
Regarding the Star Wars spinoffs, not much is known about the plots or even what characters will be featured. It has been stated they will be origin-type films possibly spotlighting Yoda, Boba Fett, Han Solo and Obi-Wan Kenobi in individual movies.