Microsoft has already confirmed its intent to bring microtransactions to Sea of Thieves, Rare’s upcoming shared world action adventure game, shortly after it launches; however, it seems that some, though not all, items that you can purchase with microtransactions will also be earnable in game.
Speaking to Metro GameCentral, Rare’s Executive Producer Joe Neate confirmed that this is something that the developer is working on, though it is not yet at a stage where it feels comfortable divulging details, or committing to them. He also confirmed that Rare is looking to support the game fo a very long time- though that was laced with the caveat that it will be supported for as long as people play it, which can go either well or not- since the industry is full of examples of games with low player bases having their support yanked from them early and prematurely.
However, Sea of Thieves looks absolutely fantastic, and hopefully, it achieves the popularity that it looks like it will deserve, and continues to be supported for a very long time to come.