Why? We already had a full character arc for him already?
Despite several other ppl already being right about why a Thor4 is a good thing, I gotta say this is completely false.
What full character arc did Thor have?
In Ragnarok, his dad died, he got his eye gouged out, his sister broke his hammer and beat his ***, killed his friends, gets enslaved, and to end it the only way he can beat his sister is by letting Surtur destroy Asgard as the surviving Asgardians are basically refugees.
Then half of them are killed by Thanos in Infinity War and his best friend and brother are murdered in front of him. He comes up with getting a super weapon made to kill Thanos and after wasting so much time doing that he's literally late to kill him as Thanos kills Avengers and completes his gauntlet despite both being on the same battlefield. Then the snap takes another half of the remaining Asgardians.
All Thor got in Endgame was a motivational talk from his mom to get him out of his depression which was caused by his inaction and empty killing of Thanos. Son didn't even get to vent. He didn't get a showdown with past Thanos, didn't sacrifice his arm and do the snap to bring everyone back, didn't get the gauntlet/stones and do the snap to get rid of Thanos and his army. Fam gave up "ruling"what was left of new Asgard and went to space.
Thor's character arc is definitely not complete