If that was the case, P+ would have canceled it after Seasom 3 (and if you look at SNW S3 Ep. 10 it WAS clearly written as a Series finale; meaning at the time Akiva Goldsman believed that after the increased costs due to the new SAG contract post actors strike that S3 WOULD be the last, yet is WAS renewed for a full 4th season.....There is a REASON P+ wanted to cancel it after S4 (they didn't like the direction the show was headed).
And both cast members and Akiva confirmed that it was P+ Execs plan to complete SNW S4.anf then do a series end with a Streaming film (like Secton 31 was.) But when the Producers said a two hour film wasn't enough to tie up the character stories P+ instead agreed to a 6 episode 5th season.
Trust me in that if a studio is diseased with the direction or ratings performance of a series they will cancel it rather then renew and decide to spend more money producing new episodes.
Also, you can guarantee that if they d8d renew 8t but were still displeased with its direction/type of stories - they'd give the Producers LOTS of production notes and Edicts to follow; but all reports indicate this type of thing ISN'T occurring.