Umm... May I begin my thoughts?
1) Character Revivals - I would really love having all the classes from all the Etrian Odysseys again, as you can do a mix and match that'll make parties unique in their own way. Also, you can import characters from Etria, Lagaard, and Armoroad (Or EO, EO2, and EO3)
2) Return of NPCs - I loved the NPCs in EO3, and I bet people would have similar feelings for the NPCs in the EO linup.
But if they can't do the return of the npcs, then I hope the NPCs in the possible next EO game would be just as likeable for me... I dunno though,
Not everyone likes Etrian Odyssey for their NPCs...3) New Classes - A lot of people were saying they didn't like the classes for EO3 (I was pretty fine with them. For me, battling with EO/EO2 classes was harder for me...) So I hope they can make new classes as well just because the concept of playing as a Cowboy makes me giggle, and not only that, but playing as the Deep Ones and Kupala's Race (forest creatures / Forest Folk )
4) Possibly what everyone else wants...
Because they all sound so cool.