I've not heard a word of this and if true, its just plain ridiculous. This isnt the Raiders, Redskins or the Cowboys and I remember it took Cowher a few years to reach his first Super Bowl. The Rooneys have quite the good track record of hiring good HCs so I have no doubt in Tomlin and his abilities.
If you are one who believes Tomlin should be canned then, in my opinion, you obviously arent a Steeler fan because that is not how it works for this organization. The Steelers win with true talent, not $$$ and that takes a little time. From my count, the Steelers are traditionally a pretty good team.