I have received several emails stating that Chris Jericho's band, Fozzy, is not scheduled to perform at the Rock Star Uproar Tour on August 19th, the night of SummerSlam. The band has actually not been scheduled to perform on that night for awhile now, so if they were listed as appearing, it was a misprint.
Jericho still appears on WWE's listing for SummerSlam. He is also advertised to appear on RAW the following night on August 20th on the website of The Save Mart Center in Fresno, CA. The arena highlights Jericho's appearance on their site, which is likely his last appearance of his current WWE run.
As noted earlier, Jericho also confirmed on his Twitter that he would not be appearing on WWE's tour of Australia, which starts at the end of August.