CBS has already said it isn’t bidding. How much inventory and money do Fox or NBC have to offer? I guess Fox could try to go huge on a prime time Saturday night game but thats probably it.
The current SEC deal is locked in until 2034. Who knows who will be in charge at these places by then? Whatever CBS and NBC and Fox say right now doesn't really matter and frankly, they need to sound 'all in' on their current partners, so I'm not surprised to hear them say they have no interest in pursuing the SEC. Just keep in mind that means "right now".
As far as real estate goes, CBS and NBC both have fledgling streaming platforms and have been streaming live sports on both of them already. There's no reason they can't leverage those platforms to take on more. In fact, Paramount+ specifically could use more sports content.
Fox is a little bit of an odd bird. They sold off their regional coverage to Bally and they haven't come out with a viable direct streaming service (I assume since they sold their entire entertainment catalog to Disney and still have some sort of distribution deal with Hulu for their live shows), so they pretty much only have their local stations and FS1. I'm not sure how much they can squeeze into those two. Maybe some of their OTA alt channels? I'm not sure how much of those are nationally owned vs locally owned though.