Fortnite is a game that undergoes frequent updates so week-by-week you can expect to see patches which either squash bugs or make small changes to gameplay that improve the overall game experience.
In the long term, Epic Games has announced that it's looking to make some game-improving changes. These will include more Limited Time Modes as well as improvements to performance, quality of life and the games replay
system. Players who prefer using controllers will see improvements made building, as well as the ability to turn of aim assist while building for greater accuracy.
In terms of Limited Time modes, 50v50 might hang around for longer. However, a new Limited Time mode called Playground could be in the works. This mode would take place in the usual map but it'd be longer with more resources to hand.
We can also expect to see more interesting Limited Time items like the recently introduced jet packs in the future.