With most video game franchises is not that difficult to estimate when the next game in the series will be released since you can take a look at their release pattern. However, this thing does not apply to Fallout.
The first game was released ten years ago, back in 1997. The next one was launched soon after, after only a year. Then, fans had to wait ten years for Fallout 3, and during this time there have been other two spinoffs. Fallout New Vegas was released two years after Fallout 3, and Fallout 4 was launched a few years ago.
When will Fallout 5 be released?
If you take a look at the timeline you can immediately realize that is very hard to guess when the fifth installment will hit the shelves. It could happen next year, or we might wait several years for it. However, there are reasons to believe that players will have to wait a while in order to receive this one.
We are saying this because there have been no signs or official reports that indicate the fact that Fallout 5 is in development. Right now, it appears that Bethesda is concentrating on Fallout 4 VR and on some other projects.
Therefore, it appears that Fallout 5 is not their number one priority at the moment and they are not planning to begin working on it anytime soon. We will have to wait and see how Fallout 4 VR is received by gamers and only then we can begin speculating about Fallout 5.
Nevertheless, it is very likely that the project has not even begun, which would mean that it is very likely that we will see this game sometime after 2020.