The folks over at Platform Nation have kicked out a list of additions and tweaks they'd like to see Bethesda implement in their next installment to The Elder Scrolls. Assuming there will be another non-MMO installment, anyway:
A return to Morrowind will suffice for this I think. Fallout 3's leveling system is Fallout, not the Elder Scrolls, but in Oblivion there were alot of faults. I think we need more varied skills, like Morrowind. Oblivion was dumbed down in that Blade encompassed many different weapon types. I want to see the return on Long Blade, Short Blade etc.
On the subject of leveling is also the world itself. I think after Fallout 3 Bethesda will go back to Morrowind, making the world static, and the character evolving around it; not the other way around. I want to be able to know I can't handle a certain region of the world yet, go away and train, then come back and kick some ass.