The upcoming Monster Hunter: World expansion titled Iceborne will be the game's final expansion, Ryozo Tsujimoto (producer) revealed in a recent interview with Game Informer. This fact isn't overly surprising, considering the game was officially released in January of last year, but it seems a good note to end on nonetheless. Tsujimoto also explained that the new Master rank system is similar to the "G rank" that Monster Hunter fans are used to.
Apart from this, Iceborne, being a massive expansion is going to be supported with updates much as the base game has been.