My understanding (based on a link that I found a few days ago; sorry I don’t remember where for sure, but I seem to think Fox News) is that the mainline series will continue, but that McCoy will be made the DA to replace Fred Thompson’s character. The “real life” reason for this is that Sam Waterston costs too much for them to keep giving him so much screen time, so they will hire a younger actor to take his place doing the heavy-lifting on the show.
In general, I’ve heard that of the franchise series, SVU is in the best shape for the future and that CI is in the worst shape. I believe that original episodes of CI will now air on USA or TNT, not NBC.
Anyway, that’s what I understand.