I don't think Patrons *can* revoke the powers. Though breaking your terms could result in a punishment? Like
the one Wyll faces once he faisl to do Mizoras bidding.
What I wonder is if we will have some choices regarding the nature of our Patron. I mean, there is a rather hefty difference between the Archfeys. Titania has different interests then the Prince of Frost.
Though having a real punishment for breaking the pact would actually be great - though the punishment mostly means that you can no longer level up as a Warlock.