Contract lookthrough in terms of $.

What's better to renew a contract directly at start of the season when he has 2 years left, or to renew it next season?
I've messed up a bit and now my cap asks for 36K per season.
Thinking what to do...

You'll pay less in wages if you wait until the next season to renew the contract. Remember, you must not assign any skill points during the season for this to work.

So, If I have someone who has 1 year to go with ? he'll leave within 7 days if I don't renew contract, right?

no, he will only leave within 7 days if, and only if, he is without a contract. If you let the contract run out, zero years, then he will be 15% cheaper to resign and you have 7 days to do this