If the coaching staff were still the old Houston squad I would certainly say Morency. The problem is we're talking about an offense that Dayne already knows: Kubiak's offense.
First off, I expect Lundy to be solid, although unspectacular. If he doesn't do well I will actually expect Morency to get the backup role, although Dayne will likely get some action. Assuming Lundy is injured or is ineffective, if Morency doesn't show up I think Dayne will definitely get looks merely because of the head coach's familiarity with the player.
Kubiak wouldn't have signed him otherwise. I have no information to back this statement up whatsoever, but I kind of wonder if Denver bringing Dayne in was Kubiak's idea to begin with and that's why Shanahan wasn't in love with him during the preseason.
From a mere standpoint of all the information I've read I have to go with Morency, but honestly my gut is telling me Dayne.