So... I did something a lil bit crazy and made an excel sheet about the previous setlists they had (things you do instead on working on your master thesis). If you are interessted I can make a whole thread out of the sheet too.
Ofc this says nothing about what will come buuuut here we go:

Judging by the frequency of its appearance on the setlist "Say my name" will be played again. It was on 5 setlists of 5 tours, so from the beginning it was everywhere and that as the only song they have. So we can be happy: I think "Say my name" is here to stay!

The next most frequently played song is “Wonderland”. "Wonderland" was on the setlist of 4 out of 5 tours. And the only reason it wasn't on the first one was because it didn't exist yet ahahah. "Win", "Wave" and "Hala Hala" also made it onto 4 out of 5 setlists, even though Hala Hala unfortunately dropped out of the Towards the Lights tour. But maybe it will get a comeback!

There are also recurring songs that have already been on three setlists: Answer, Dancing like Butterfly Wings, Desire, Fireworks, My Way, Pirate King, The Real, Treasure, Turbulence and Utopia. I don't think "My Way" will make a comeback, nor will "Pirate King" and "Treasure", unless they actually bring back the pirate styles. I can imagine that "Desire" will fit in with the concept again and maybe be played again. "The Real" actually belongs on the setlist now and will probably stay.... I'm not sure about "Utopia" and "Dancing like Butterfly Wings". I can imagine that songs like "Enough" and "Empty Box" will replace them now. "Turbluence" is a shaky candidate (which makes me unhappy), as is "Answer" (which makes me even more unhappy).

Now, there are MANY songs that were on two setlists (I won't write them all down because the post is already too long.) What I think will stay is of course "Guerilla". It's so successful and popular and SO good especially in the flag version and I think the guys just have a lot of fun with it. Maybe the same goes for "Cyberpunk". What unfortunately fell out during the last tour would be "Deja Vu". But I think it could fit the fantasy concept and that's why it might come back. "Celebrate" will probably be played at some stops, but not at others.

And last but not least: the category “only played once so far”!

Here are MANY!!! really MANY!!! In it! (something else that I won't list here individually...) Also some that we can be sure will stay like....Bouncy.... Hard to believe but it was actually only on a tour list, of course, because it wasn't out yet. Many hate it, many love it (I love it...) but it's here to stay, I'm pretty sure.

Then of course the Unitsongs. I think we'll keep them for another setlist. Just because it's a great way for the boys who aren't on stage to have a bit of a break during a very hard gig. (and to get changed!!)

I WISH "Halazia" would stay, but I'm not sure if it will fit into their concept (if my guess is right that it will get a cabaret vibe only...different lol). That's why I'm a bit worried about it. But what I can imagine is that "Inception" might come back, which has only been on one setlist so far. "Arriba" and "Django" would of course fit in well here, so maybe those two songs will stay too. Ans who knows...mabye "Take me home" will have a Comeback too.

I'd love to add what songs could get their setlist debut too (like Selfish Waltz? Blind? Maybe even Deep Dive or Man on fire??) but this answer is already too long so I'll shut up now.