Yes, that is how it would work. When you call at the 7 month window, there is no fee to change from your home resort to another
DVC resort, providing there is availability to do so.
In your example, your July 2011 trip, would fall in your June 2011 UY. To "pay" for that trip, you can use points from June 2010 UY that you have "banked", any of the current 2011 UY points, and can also "borrow" from your June 2012 UY.
Many members do book at 11 months at their home resort first and call right at 7 months to change. This way, you know you have something if what you want is not available.
Good luck!