Kurds and Shia invading Sunni territories will have the opposite effect and will be viewed as land grab by the Sunni populace.
I wouldn't want them to invade, if you want to take down a beast like this it's all about divide and conquer. A strong Kurdish country would alleviate some regions in Iraq and Syria and cost ISIS their supply lines from east to west. It will also make ISIS lose land and bring quite a stable government of Kurds into the mix. With a stable government sectarian violence gets sprung to a halt and could eventually even be relinquished, if we managed to do that at least in the Kurdish territories, that's already a victory to the world.
And since Kurdish are Sunni, it might not get such a nasty sectarian outrage over it as well.