What are the chances that they do prosecute for felony DUI ten months after the incident?

I was pulled over in October of 2012. I did not realize it but I had a suspended license for 6 years for an unpaid ticket that I was unaware off for lapsed registration. I had been at a party and had been drinking. I blew .13. I was below extreme. I was arrested booked and released the same evening. The arrest happened in Arizona. Because of the distance, I had several motions to delay the arraignment. I finally requested a court appointed attorney and was told verbally over the phone that I did not qualify and that my pre-trial was in 30 days. Thirty days later, I called in to the County Attorney and he told me that the case was being dismissed and that I should not worry about this any longer but that he was referring the case over to another attorney for a felony DUI because of the license being suspended. However I might never hear from them again. Last week I received a letter from the courts stating that the DUI was dismissed and that they were investigating for Felony DUI. Why would this happen? I was ready to plead guilty and take any deal and be done with it. This just seems too good to be true.