As noted earlier this month, Chris Jericho's band, Fozzy, will be performing during the Rockstar Uproar Tour, which takes place from August 15th through September 30th.
One of the tour dates is August 19th, which is also the date for SummerSlam. WWE currently has Chris Jericho listed on their event page for the pay-per-view, so it remains to be seen if he will appear on the card.
Jericho is not advertised for any shows (with the exception of SummerSlam) from August until the RAW Supershow on October 1st from the Chesapeake Energy Arena in Oklahoma City, OK. He is also advertised for the WWE overseas tour which starts in late October.