In the comments was another person who the exact same thing happened to and after he removed all the adsense his rankings in google came back.
Not to beat a dead horse, but are you SURE it was the EXACT same thing? That their sites were DEINDEXED from google? Not just lower rankings / significant drop in traffic, but removed from the google index?
Because as far as we know, there is a BIG difference between having your rankings / traffic tank, and being kicked out of the index.
Also, even if you do find a way to monetize your site without being dependent on Adsense, how will you be getting traffic to your site?
I am not trying to be a bummer here. I just encourage you to really take a good look at your sites and see if there is something else that is causing you to be deindexed.
In fact, I would encourage you to go to the google Webmaster tools forums and list a couple of your sites there and ask why you were deindexed. You will get some haters that will tell you that it is XYZ, and what they tell you may or may not have any bearing on reality. But you will probably get at least one person there who will look at your site and offer some good advice.
You might even get a google employee to look at your site and give you advice.