EDIT: to clarify, I am talking about trait books. Skill books won't happen, but maybe some skill points trainers can happen.
I have considered this for some time, yes. I don't rule out the possibility of giving 3 points after level 12, and 4 points after level 20.
However the increase is not supposed to be proportional or linear. The system caps at 10, and I might introduce some advanced skills with requirements of 9 and 10 so only very specialized characters can reach them. And there's the books, which will probably be around 15 when all is said and done.