My biggest hope for the Ultimate 4 is that they can serve as proper foils to the 4 main Applidrivers. Consider that --
-- Globemon and Charismon possess clear design parallels to one another (Wikimon even lists Charismon as a sub-species of Globemon).
-- Revivemon and Biomon possess some mechanically similar abilities.
-- Beautymon's singing and dancing abilities could be a nod to Eri's idol status.
-- OK, I'm having a hard time finding a parallel between Fakemon and Astra & Musimon, so I'm gonna focus on him being an "evil clown" -- Astra is the designated comic relief character.
So my hope is that, considering the perceived magnitude of a God-grade Appmon, and the Ultimate 4 being hyped as key participants in the next arc, there will be more time spent developing them as foils or rivals to our heroes, than the fusion partners for Super and Ultimate grade, which were largely featured as Monster of the Week characters (Navimon, Timemon, and Coachmon withstanding -- but I think their contributions as recurring characters is decidedly mixed).