They said the Tyr stuff ends with 10.2 so I don't think Ellisande will be any more than a quest.
I don't think that DF was canceled, I think it was genuinely planned to be shorter "filler" before 11.0. I know it's seen as BS by many that Blizz planned Shadowlands to be short, and I think that may truly be BS (though besides the Drust there was nothing really to do) but the second Iridikron left DF kind of ended already.
That, or we just aren't getting 4 raids anymore. I wouldn't be surprised if they confirm shorter expansions from now on, especially if we get F2P confirmed next expansion.