Whereas I can't see the writers doing something as creatively lazy as just giving Coulson another resurrection. A lot of the show has been about Coulson dealing with the consequences of his first resurrection, and they finally brought his story to a close in a meaningful way. I can get them not wanting to lose the actor, but bringing the character back from the dead a second time would be a cheat.
It sounds more like Gregg will be playing a very different character; even if it is something like an alternate-reality version of Phil Coulson, he'll still have a very different personality, and it sounds like Gregg relishes the opportunity to play something different after so many years. That kind of change is a challenge that actors and writers tend to enjoy, so I don't see any reason to doubt them when they say that's what they're doing.
