raising the cap was addressed by Mark 'Chiefshade' Steelman on the UO Facebook page on 6/24: (question from player in bold)
Just wondering has there been any discussion on raising the skill cap too 800? I mean you know after you raise or get your character to 720 there is only so much you can do. I played UO and tried a lot of other games over the years ,but always came back to UO until (No Flaming or attacks please) WOW came out. I think / know that one thing about wow is that you know expansion time you can go back to your old toon and start going to the next 10 levels. I would greatly enjoy building a new skill on my main character on uo. If said skill were to be raised to 800.
A:
To answer your specific question, yes, there has been a LOT of discussion here about that. However, after many discussions (sometimes arguments) it was decided not to do that.
What we do have is 3 new skills in which you can respec into. We have a craft skill, Imbuing, a ranged skill, throwing, and a magic skill, mysticism. We are hoping that players will enjoy coming up with new specs based on these abilities.
I feel that the main reason we haven't extended the cap is because some of the existing skills are really kind of unballanced and the fear is that a raised skill cap will exagerate the problem. As it is, many raid encounters have been reduced to single player encounters for people who min-max their spec to the "right spec". In a game like UO, it is a shame to give the player so many choices and then make a few vastly superior to the point where players feel there is a "right spec" and a "wrong spec" and some skills that are "required." We want to fix that first.