Contrary to all of you, I don`t plan to work on a 50,000 word novel, but I might not be able to resist the temptation to try (and I would most likely fail).
My plan is to focus on short stories - finishing unfinished stories and starting unused ideas. I think it would be much easier to reach the 50,000 word mark that way, but that`s not the point - I want an excuse (I`ll keep track anyways).
I thought on a similiar idea for a world I plan to sometime use for some RPG system. Humans can cast very specialized magic after much effort and training, but to cast spells of many types you have to somehow convince a magical being to give you the initial power. You can train your powers normally after that.
I actully think it`s a good thing. I take a minimilist approach to writing, I don`t like when plots and descriptions stretch, but I do tend to take it too far (which makes this challange even harder for me).