Bethesda seems to be leaking those rumors, much like the leakage of radiation in the Fallout universe. And this rumor, well it just might mean a brand new Fallout game.
Via the official twitter account, a "Please Stand By" message plays on loop. The psychedelic coloration suggests that this is likely Fallout 5, as each game has had a distinct color scheme for the same loading message. And what a color scheme. No more drab grey. This one is Technicolor!
Bethesda is probably trying to get some buzz (grab some Jet, maybe?) ahead of E3. It's possible that this could be simply a remastered Fallout 3, as it nears it's tenth anniversary, but if this really is a new game in the series, it would not be surprising for them to announce it in this way at E3. For Fallout 4, the studio announced the new game at E3 in 2015, with a release date of November later that year.
This new tweet bodes well for fans of the franchise; we may be getting a new game soon.
So brush off those vault suits, grab a companion, and (hopefully) get ready to log another 200+ hours in a post-nuclear world. After all those hours invested, tell me I at least get to bring my dog.