User blog comment:B214/High School DxD EX/@comment-4547267-20150828180103/@comment-3965848-20150828181654

Isn't EX like a future that was going to happen to the main plot, but was changed by the kids coming back in time and creating a different and better future for them.

Which would lead to me guessing that EX2 could possibly be a newer canon future for the main plot.