Middle-earth: Shadow of War is set to release in August but very little is know about the game. However, according to the Steam page, the game will include "in-app purchases" which translate to microtransactions.
Middle-earth: Shadow of War's Steam page doesn't elaborate on this but it's likely to be the "war chest' available in the special editions of the game.
This isn't a new concept as games like Assassin's Creed Unity and Deus Ex: Mankind Divided are a few of many games that offer single-player microtransactions. If WB Games does decide to put microtransactions into Shadow of War it's likely that the game will feature more weapon types with varied attributes.
We won't have to wait much longer as a gameplay trailer is scheduled for this month. Perhaps we'll get an answer during its reveal or at E3 2017.