Datamining has revealed the Mythic+ affixes that were added to Season 4. In addition, the Afflicted affix had its punishment increased.
In addition to the the Season 4 dungeon rotation, all of the 12 affixes in Season 3 look to be returning as they have added them to the upcoming season.
As a reminder though, the 3rd affix would now only show on +10 and you should still be able to get Myth gear without doing the 3rd affix.
From datamining, it looks like there's only one change for affixes this patch. However, there could still be more than are not dataminable.
It's unclear exactly why they made this affix harder when this affix was already punishing when you failed to do it.