To be honest, I think it's going to happen. A big factor being this is what the UFC want, so it's probably going to happen. Hypothetically speaking, if Dana White says that Pettis is getting the next shot, what does Edgar do? Sit out to get the next shot, for what could be the best part of eight months, risking out of sight, out of mind? Take a fight in the meantime against one of several world class lightweights and risk losing his only card (that's he's a top ranked lightweight himself)?
I remember having a similar discussion online with someone a while back who was adamant that Demetrious Johnson wasn't going to go to 125lbs after he lost to Cruz. His reasoning? "Mighty Mouse doesn't want to. He said it himself". Then look what happened. Those defending Edgar at 155lbs either say he said he doesn't want to (it doesn't matter really, if Dana says drop down, now he hasn't got the belt he doesn't have many options) or that he deserves a rematch (maybe he does, but like many have said, it's not clear cut and Pettis almost certainly will get it).
End of the day, lets not forget that he could easily flit between the divisions. Say he goes to featherweight then loses to Aldo, he could easily blame the cut and go back to 155lbs and still be in the mix. I say, if you've got a title fight on the table and you're coming off a loss, he'd be stupid not to take it if he's not getting the rematch at lightweight. Regardless of all the talk of wars and broken noses, he's got the chance to join a select club of fighters.
Like Dana said, they can't force him to drop down, but they can heavily persuade him.