Ryan Alosio, who provided the voice of Deacon in Fallout 4, let the news slip on a post he uploaded to Instagram.  Alosio said: 

Alosio deleted his post soon after, but not before FragHero took a screenshot of his post:

While this is still a rumor, it may not be one to take with a grain of salt.  This may seem hard to believe, given how long the wait was between Fallout 3 and Fallout 4, but Alosio could be referring to a Fallout game in the same vein as Fallout:  New Vegas.  New Vegas came out just two years after Fallout 3, and now that Bethesda is familiar with the next-gen consoles, a new Fallout game coming soon may not be as far-fetched as it sounds.