So, the parent company of Bethesda Softworks filed a trademark request on 09/10/18 for the name Redfall, with the Good and Services description filled out as “Computer game software for use with computers and video game consoles”. While that could mean any number of things, the most likely conclusion is that it pertains to title of the upcoming release of Elder Scrolls VI game announced at this years E3. The game was announced at E3 without a title and very little info, but the theory makes sense, unless it is a Elder Scrolls Online title or DLC or some other game completely.
Regardless, let the speculation run rampant through the development cycle of whatever this turns out to be.