Recently, Tucson has voted to recogize Vail as it's own town, even though it is not incorporated as a town. This was to let the people of Vail know that if they form a town of their own, the City will not oppose it. They even said they encourage incorporation and the organization of a town government.
Expect to see big changes in Vail over the next few years!
Once a town incorporates, it needs funding and seeks to increase it's tax base. It does this in part by annexing neighboring areas.
Looking at Oro Valley, a community to the North of Tucson, it has grown 10 fold to 45,000 people over the last 20 years.
Best of luck.