|Looks like next year's Milwaukee IndyFest will be August 22-23.|
This Journal Sentinel article suggests that next year's ABC Supply Wisconsin 250 at The Milwaukee Mile will be held August 23, 2015.
Apparently, a central consideration is next year's Wisconsin State Fair which runs from August 6-16, a later date than this year. The later date for next year is because Labor Day in 2015 will be essentially a week later than this year. Like this year Milwaukee IndyFest in 2015 will try to run one week after the conclusion of the Wisconsin State Fair.