Steiner returned at the most recent tapings and Nash, despite his constant denials on Twitter, stated in an interview just last week that he was in fact renegotiating his deal with TNA.
And as for Sting - has anyone heard anything about his contract status? No. That could be taken 2 ways - he hasn't resigned or he has. If he hadn't, I'd think there would be reports of WWE trying to negotiate a HOF induction with him. The fact that there hasn't been a single word about him since his departure, to me, means he's already resigned and is just awaiting his return angle.
The only person not accounted for is Booker and, really, who needs him?
If TNA honestly let Nash and Sting walk out the door without putting someone over and have no plans to bring them back, then they are, in fact, even dumber than anyone has ever accused them of being.
TNA isn't creative enough to come up with an angle to structure current young roster members into a unit to contend with Immortal - a rehashing of an old angle and an inlfux of 40+ year old guys is exactly what everyone should expect.