Sparano never should have survived that Week 17 debacle in 2010. The team could not have possibly sent a louder message that they were done with this system, this regime, these coaches. Yet, Ross and Ireland didn't listen.
But, now that Ross made the decision to stick with Tony Sparano, and even gave him a contract extension, IMO he needs to keep his word and actually let Sparano coach as long as possible without risking who we can get to replace him. Dave Hyde has pointed out that in 2003, Wayne Huizenga wanted to fire Wannstedt but didn't want to do it during the season, and as a result of waiting for the full season to play out he felt like he missed out on the guy he wanted to replace Wannstedt with, and so he stuck with Dave in 2004 in that weird shared power situation with Spielman. The result was awful. But the situation does show that it's possible you may need to get rid of a guy before the season is quite over yet. Outside of that, Stephen Ross needs to focus on being a man of his word.
He already screwed up with the Harbaugh episode. Don't make it worse. Otherwise, who will really want to work for you?