I know that WotC haven't done it when they have released new material but I think that we should have hybrid rules for our classes in the book. It would make our book stronger and would hopefully see more play time. It should be a seperate section at the end of the book, like it is in the PHB3, that covers all of the classes and the new Assassin build.
As another note, people should be thinking about how their class would work as a hybrid class as they are making the class features. There's nothing worse than having to go back to the features and tweak them all because there was no way of hybridizing them.
Note 2: We will NOT be "printing" the Assassin hybrid, or the standard Assassin, rules. It would be agaisnt the T+C of DnD Insider and we would be sued. We can however point people to where the Assassin can be found, much like the little grey box did in PHB races: Tiefling.