Again though, this is all guess work. It's taking a throwaway, slightly teasing comment from Sly as Gospel. What about the other countless names Sly has name checked but haven't signed on?
I've no doubts Sly wanted Seagal on board. Whether Seagal wanted to come on board is another matter. But as said before, if you look at this think logically, there's a good reason why Seagal probably never got an official offer. That is Avi Lerner and Millennium films.
There's too much bad blood between them. I believe Seagal still believes he's owed money from them. I also believe Millennium feel like Seagal owes them money.
Until either party budges, which is unlikely, then no matter how much Sly may have wanted it, it just won't happen. Sly also doesn't sign the cheques.
I think Seagal would probably have been on board if not for the history between him and Millennium. He did Machete after all. His ego wasn't too big for that.
And you should also believe that if Seagal had been given a direct offer and turned it down, Sly would tell the world. He did so when JCVD turned down the first film, and also did so when Willis asked for too much money. If Seagal has turned down a genuine official offer, we would know.
Seagals made a lot of bad career decisions and his next film does sound awful. But in this case I'm not getting on his back too much because it was always going to be unlikely that he'd get an official offer. We also don't know from the terms of the court case of 10 years back. It might actually not be legally possible for Seagal to work for Millennium films again. Something could be done to fix that, or an agreement could be reached by both parties but it would be a long drawn out affair and too time consuming. Too much trouble just to get him in as a supporting player/cameo.