I am a fan of both fighters. Cheick has an exciting kick-boxing style. He hits strong and fast and looks pretty technical. No matter how much he has trained on the ground game these past few months, he will rely on his stand-up. Anyone who saw the Cheick vs Assuerio Silva fight knows without a doubt the weakness of Cheick's ground game.
Mirko has great take down defense, and has been training with Werdum (who beat Gonzaga a while back). Werdum is a top BJJ fighter. I have to conclude that Mirko's overall experience, great takedown defense and better training in the ground game overall means Mirko's ground game will be far superior.
So then the question becomes the stand up game, and the submission game. The submission game will be non-existant as neither fighter is very good at submissions and save for a rear naked choke neither will be submitting the other.
Now the stand up is what makes this fight compelling. I think both have knockout power, but it will come down to momentum, who can put together a string of hard strikes quickly, accurately and consecutively. Mirko is the harder striker, and has absolute knockout power in his legs. Cheick is younger and seems to be bit more athletic. I also think he isnt likely to gas out (Mirko has had issues in the past with cardio).
If the fight is a slug fest and it goes 2 rounds or less, Mirko should ge the KO. If the fight goes to a third, look for Cheick to have a strong third round with an outside shot of a ground and pound type victory. Absent a lucky ground and pound, I see Mirko learning his lesson and chopping Cheick's legs until he can get a few body or even head kicks in there. I see a good chance that Cheick will get knocked the heck out if he is unable to stop the leg and body kicks.
Overall, Mirko wins in most scenarios (ground scenario, points, ko), Mirko might lose if Cheick can get a few strong consecutive strikes in there, or if he traps Mirko against the cage and gets a ground and pound situation until the ref stops it. If it goes to decision Mirko should win.
This should be an exciting fight!