Remember what prompted Celestia to decide to get her and Luna to retire is apparently Equestria experienced a long time of "peace" since a long while?
Imagine how hilarious it would be if Discord's plan backfired and ended up basically scaring either sister out of retiring.
I mean, with how peaceful Equestria apparently had gotten, the moment the sisters decided to retire... BAM, a villain who's supposed to be dead came back and caused trouble. At such a seemingly strange timing too.
That right there might cause either sister(maybe especially Luna) to go "maybe retiring isn't a good idea.." or end up taking it as a sign that they aren't suppose to retire.

Just imagine how hilarious Discord's reaction would be.

7216486
You’re literally laughing out loud, aren’t you?

7216493
Maybe.. \ovo/

7216495
Awwww... thinking of how Discord can hilariously embarrass himself... I can imagine that.

7216502
Surprised that didn't happen in the show.
Like with either sister beginning to have second thoughts about retiring.

Discord would certainly freak out for sure, lel

7216486
THAT WOULD BE AMAZING HANDS DOWN!

Besides, it would finally see some sense in why Celestia and Luna shouldn't retire in the first place!

It would be funny to see Discord feeling ridiculous as he just freed three other villains.

7216656
And how awkward he felt with what he had just caused to the Crystal Empire, Spike and also the Tree being destroyed(or at least rendered useless since it didn't even appear in the finale. Pretty much its spirit is now powerless to do anything pretty much.).

7216661
Don't forget my reply. ^^;

7216669
Whoops. Sorry

Kind of wished the season 10 comics touch on the issue of the sisters retiring like that.
Still not fond about Luna retiring

7216685
It's k :)

Yeah, hopefully my idea would be this for the comics: Celestia and Luna come back, decided that it was wrong for them to retire, and regain their proper spots, and thus the ruling system would go back to being balanced with the 5 Princesses! (Yes I count Flurry Heart as a princess anyways. :/)

How's that? :)

Yep, it's like Hasbro forgot about what Luna did prior to the events of the show. Good Grief.

7216695
It felt like there should be a bunch of issues for Luna there but it all got brushed aside.

7216703
Agreed.

Sometimes I just wish this stupid arc in Season 9 never happened at all. It's just pointless to bring up something Lauren wanted for Twilight when the show was in development even when so many things have changed since her original vision. -_-

7216707
If they wanted to honor Faust's original idea, the big question would be did she intended for Luna to step down too or would Luna co-rule with Twilight? I don't think she mentioned anything about Luna's fate in her original idea there.

7216710
And of course the bigger question: Did she even WANT Twilight Sparkle to become an Alicorn in order to be ruler and fulfill her original vision? :/

7216713
Not sure

I wonder what Faust even planned at all for Luna's case in general.

7267609
Same