The potential NRL coaching merry-go-round is Bennett to the Tigers, Seibold to the Broncos, Cleary to the Panthers. That leaves Souths in the cold, which is why the rumour is of them looking to Furner to take over.
All of this could happen, or it could all fall in a heap. Its a huge leap for Seibold to go to the Broncos, as replacing Bennett comes with huge expectations and the potential risk of your reputation being smashed as a result of not coming up to scratch, and he has a long-term contract at Souths on the table. There's also no guarantee the Tigers will release Cleary (as an aside I'm not sure why the Panthers are so obsessed with him as coach except for keeping Nathan happy).
Regardless, if it happens then we shouldn't try to force Furner to come to Leeds. Accept it, act professionally and move on. Demetriou would be my next choice, as he's very highly rated at the Broncos. Apparently Seibold has until next Wednesday to decide if he wants to stay with Souths, so we could be kept waiting until then.