Is that Luna could be setting them to share a dream, so they're conscious in a dream world and comically fighting each other. Partly for their "true" punishment being together forever, but also maybe leaving open a chance of redemption.

And perhaps from there, maybe after several years, they come to accept each other as friends and truly open their hearts to the magic of friendship, at which point Twilight would enter their dreams, realize their redemption, and release them.

(If someone wants to write a fanfic of this, feel free, I probably won't as it won't be my headcanon but I know plenty of you didn't like that and would probably be happier thinking this)

Also, G5 is likely either going to retcon Season 9 (maybe 8 as well) or release them, probably for redemption if that's what the movie's synopsis means by "making new friends out of old enemies". I mean, G5's writers will have to have seen all of G4 if they want to be consistent, they're probably bronies and pegasisters already, and chances are they either didn't like those seasons or want to pander to those that didn't, or at least were upset about Cozy Glow's (maybe not so) final fate.

Though there IS also the chance that Cozy Glow's the one who drained the magic from Equestria in G5; that Luster felt sorry for her and released her in the hopes of trying to reform her, but she backstabbed her (perhaps literally) and took over Equestria.

7452392
It has been stated that Twilight nor any of the Main Six would not be returning in G5. Considering the different styles in animation compared to G4, I’m highly doubtful now that it’s a sequel in contrast to a reboot.

7452422
Everyone's pretty confident it will be a sequel (arguing with the theory it'd be a reboot similar to Digimon Tamers), and the Mane 6 are dead of old age.

If what you say is the case though, awesome that the Mane 6's work wasn't in vain.

Wait, is that what the synopsis said? Sounds plausible, but that would make such fanfics no longer a headcanon unless you accept it as an alternate timeline.

7452422
Source?

7452673
I didn’t find any sources to know this. I heard it from someone on here.

7452712
Then it's a rumour.

7453186
More like something that was picked up from Equestria Daily, really.

7452422
Did they say anything about Spike or the Royal Sisters though?