Who knows. We don't know where they're at internally, we don't know what features are coming in 8.0 that might consume so much time and testing like Legion's class changes and Artifacts. Different bloke running the show at the top, different people throughout the team; output of content has obviously changed with Legion so it's likely to be seen in testing.
I would love to see them drop Alpha in December with Beta in February and it for to be released in June/July. But I'm not getting my hopes up for it; a 7.4 patch before prepatch would make me okay with an August/September release.