In 2021 when talking about cross-faction raiding "coming soon" it was mentioned how hard it is trying to keep a high-end Alliance guild together in North America or a Horde one in Oceania. So most think that cross-faction guilds are the likely conclusion. Communities being newer might make it easier to implement and a good way to test if it functions well.
https://venturebeat.com/2021/11/01/w...oul-searching/
Ideally I'd like guilds to become more like sub-sections so you can better organize a community. For example community X would have a raiding guild and a pvp guild. You could belong to both for easier management. Cross-faction in general is a pretty big step for Blizzard to take so it is reasonable to think they are going to take baby steps so it is easier to revert if need be. Once you pull that ripcord it will be impossible to bring a faction divide back.