As IMJ eloquently explained, calling three singular Wonder Woman movies with no linking arc "a trilogy" just because there are indeed three of them is nonsense. Assuming it happens, it's not a "trilogy", it's JUST a series of three films. There IS a difference.
Although I wouldn't doubt they'll find a way to cram Steve Trevor in yet AGAIN for the third one, just so they can claim that there IS an arc and thus justify calling it "a trilogy".
There's also already some minor but percolating blowback to this announcement and the timing of it. A good number of people saying they may have even already seen enough of Patty Jenkins's "vision" for the character after this one's misfiring.
Hey, this'll be fun. Just to spite someone else, I'm gonna do something I normally refuse to do and post a link, just because I happen to be on the site and have it handy right now!

Skip the puff piece and head right to the Comments section for what I mean.
https://411mania.com/movies/patty-je...onder-woman-3/
It's just one site but it's consistent with a lot of what I'm seeing elsewhere. And I'll once again reiterate the fact that a good number of these exact commenters really liked the first WW movie, so it's not like they're being "haters". They just didn't like what they saw this time and aren't sure they want to see any more.