There risks of terms limits are far fewer than the risks of continuing to be governed by long term incumbents - aka, professional grifters.
The greatest risk is that it fundamentally changes the nature of our government because it sets a limit on the Will of The People. After a certain time, The People won't be able to vote for whomever they want and that's a dangerous concept to introduce into our Republic.
If you love the Constitution and the principles of self-government laid down in the Declaration of Independence, I don't see how you could support anything which disenfranchises The People.
And, before someone says it, I don't like Presidential term limits either. And, no, I wouldn't vote for Barack Obama again...unless the GOP put up another Mitt Romney type.