For what it's worth they are touting the same announcement for Edmonton's Sonic Boom as well. So any act(s) being slotted in would have to be open for two dates between Aug 29-31st.
Think that rules out NIN/Soundgarden adding 2 Alberta dates as they're booked up for the 29th/30th
So pulling a name out of thin air, I'm gonna guess the Foo Fighters. All
their website says right now is "Fall 2014" referring to the new album.
Tuesday's a good day to drop a single & announce a massive North American tour.