Mike pissed off Don too many times. No way they are getting back together. Let's look at some of Mike's actions towards Don.
1. Right after Don left, Mike announces on his very first show that he didn't like the Don and Mike show and felt it was too negative and he didn't like that and he was going to "fix it" now that he had control of the ship. On his very first show he is throwing Don under the bus.
2. The infamous Cancer Show. Here is where Mike again throws Don under the bus saying that he ordered Rob not to talk about his son's cancer because it would take away from Don's wife passing away. Mike implies that Don is self-centered and only cares about himself (even though Don was the only crew member to visit Rob and his son). He also claims that him and Buzz saved the show by doing it by themselves for two weeks.
3. Don set's up his facebook/twitter/ podcast and the very next day Mike goes on air - him and Rob making fun of D.J.'s that have to use social media to get their message out there. Rob chimes in that "only losers resort to that"
4. Then when Don gets CBS to agree to let him do an uncensored podcast - Mike bitches to the higher-ups saying that it isn't fair and that it will hurt his show. CBS then requires Don to run the show through their filters - Don kills the deal due to Mike's interference.
5. Don falls off the stage at an appearance and the whole LFF crew spends the next day making fun of him - before anyone even knew his condition and whether it was serious or not.
I would feel sorry for Mike - but he did it to himself. Mike, Rob, and Buzz should have remained professional and kept themselves in check. They can bitch about Don all they want - but he was the one getting them a paycheck. As soon as the couldn't ride his coatails anymore - they failed. To make their failure even worse - they reached back and attacked the guy who made them who they are.
Their failure is a direct result of their actions.