In an interview with Animation Magazine published on November 13th 2018 Noelle Stevenson said "“When I first pitched the show, I approached it as if had one season, but we now have four arcs of 13 episodes done. I had ideas for the big overall scheme for the show. The first thing I did was create a vision board, pulling inspiration from a variety of sources. I had the incredible luxury of working with a team of great writers. It was great to brainstorm and come up with this rich world in great detail. Get a lot of ideas and throw everything at the wall and see what sticks"
The most important part of that quote is "-but now we have four arcs of 13 episodes done". Noelle didn't specify if those episodes were done in the sense of being animated and edited or just planned and written, but I think the latter option is more likely. She-Ra is probably going to be renewed for a 5th season but I don't know if it will be 13 episodes and cover the entire 4th arc or if that arc will be split in half across seasons 5 and 6.
Noelle Stevenson also didn't specify if she intended the series to end after 52 episodes and to my knowledge this has never been clarified anywhere else.