I don't think it's Warped, Warped announcements are on Fridays/Saturdays and it wouldn't be such big news imo.. I think it's a South-American tour
Maybe..
Stephen from The Summer Set who is also announcing something on Monday, but was moved to Wednesday cleared up some rumours on twitter and he said that they were not opening for All Time Low, but they were headlining. That was supposed to be the hint of the announcement. I don't think ATL will just be reduced to an opening act so it must be some sort of big tour or festival..