It was actually true! Quite a few people were saying that Supergirl was better suited to The CW. It was never going to recapture the viewers it lost on CBS. Ratings are poor for CBS but would be good for The CW. It's a demotion though.
The MCU tie in is getting looser with each episode. It's figures have never been that great. I fear you could be right, depends how well ABCs new stuff takes off. I'm not hopeful so AOS could survive by default.
I am slightly surprised cos ABC seems on a cost cutting gig, and all the CGI AOS does, when compared to most other shows, can't be kept up for ever.