This Dev Diary from Ken Troop, lead designer on DDO: S, focuses on advancement. The issue will be addressed by introducing more moments of advancement, using ranks with Action Points and Enhancements. The whole adventure and experience of a character will be intelligently designed, and each level will be full of things to do. In the future, there may be more ranks and levels to be proportional to a D&D level 20 or higher. The strength of the Live Team for episodic content will be utilitized.

The full diary entry, here.

An excerpt about the proportions of DDO vs D&D advancement:

"Another way of putting the level equation -- DDO's 40 ranks+levels = pen and paper D&D's first 10 levels. And yes, as we expand the level cap to D&D pen and paper 20, there will be 4 ranks per level - so 80 total."