Although Bethesda is't very talkative about Fallout 4 yet, there are plans to develop the game in the near future. With DLC for Fallout 3 still in the news, it is of course normal that they are focussing on that in the first place.

They have however shared some lessons they've learned from part three in an interview. The most striking news is that there will be absolutely no level cap in the next Fallout, nor that the game will be stopped after the story ends.
Good news!

In other news: