What will likely happen is that the Big 10 with a 2nd new contract coming up for negotiation in a couple of years, will leave ESPN completely, take on a prime time CBS spot that the SEC left, keep the CBS basketball package they have, and put all their other product with FOX, including their network being there.
ESPN is going to add slots for the SEC--hard to see where since they already have them on so much, but it will be the slots where the Big Ten was.
Recent rumors have the PAC and amazon I believe being in talks. Won't be surprising to see teams moving from that conference if the financial gap grows. They are already in dire straits in that regard.
So the BIG 12 is going to have to make some serious moves between now and 2025 in order to secure better finances and good tv slots as well as an expanded streaming presence going into their next contracts.
The acc is locked up through 2036 with ABC/ESPN all rights. But if that new network doesn't feed in the money as Clemson or FSU hoped, it won't be surprising to see those two looking to exit.