As noted, it was the Jasper townsite and areas directly surrounding that have been the most affected.

No affect at all at the Columbia Icefields and further south (Lake Louise, Banff, etc). There are so many areas to hike in the Mountain National Parks that this shouldn't affect your decision on whether or not to come. Just research the particular trails of most interest and chances are they're outside of the affected zones. There's a much higher risk of smoke from distant fires putting a damper on your journey, but that's not something that can be forecasted more than a few hours ahead of time, so not something worth worrying about. Coming in September if possible has traditionally been a good time of year to visit the Rockies - fires have usually died down and the weather is clear but not cold.