Thus far, all signs are pointing to She-Ra and the Princesses of Power continuing. Late last year in Animation Magazine, Noelle stated that the series was designed as 4 arcs of 13 episodes. Shortly thereafter, some of the crew confirmed the 52 episode count, which is a pretty baseline order for an animated DreamWorks/Netflix series. There are other indications as well.
For example, last month at San Diego Comic-Con, Her Universe founder and actor Ashley Eckstein announced that she will be voicing a character on an upcoming season of She-Ra. In a recent video interview, Ashley reflected on having an enjoyable experience recording for the series, with DreamWorks and her looking to continue the partnership in some capacity. That's how the She-Ra theme for this year's SDCC Her Universe Fashion Show came to be. Ashley's character didn't appear in Season 3. So, we can deduce that her part is coming some time beyond episode 26. This is the case with Brooklyn Nine-Nine star Melissa Fumero as well. Awhile back, she mentioned in an interview that she voiced a character in one upcoming episode of She-Ra. There are also other rumored voice actors who are thought to be part of upcoming episodes.
It's not surprising that Mattel Television is producing Masters of the Universe: Revelation. Knowing what we know about Mattel's history, the intentions behind forming "Playground Productions" in 2013 (which was later rolled into "Mattel Creations") etc., as well as what we've heard from folks at Mattel like Rob David and Robbie Brenner., it makes sense that they would be producing a MOTU series.