I would love to see how they will involve the Deadric Princes in-game, but I have an idea how. It could be a special event once in a... month? week? day? I dont know, but it is a special event that will be associated with one deadric prince at a time and can reward with different rewards depending on the prince. And what is an Elder Scrolls game with my favorite (And I bet my life that he is also a favorite for many many others) deadric prince - Sheogorath? I have a special plan for this crazy beloved guy.

If Cyrodill is a place meant for PvP between guilds / alliances, maybe the Shivering Isles shall be an arena for end-game players, regardless of guild or alliance against everyone, and a daily / weekly / monthly winner shall be crowned as the new deadric prince of madness during the Greymarch, and will receive a "Sheogorath look alike" costume / Sheogorath weapon / w.e the developers want.
Another possible arena is the Planes of Oblivion, but I havent really thought this one through.

So, what do you think? If you think you have another way of involving them in-game please share it, and maybe the developers will use one of the ideas.
And another thing I forgot to mention, how do you think the developers will involve the nine (or eight) divines?

All i want to do is killing Harmenous mora.

http://www.uesp.net/wiki/Daggerfall:Daedra_Summoning Like this?