To turn out (to be) means : to prove to be
To be up to (the job) means: to be capable of doing it
To be heading (for) means : to go in the direction of/be destined to
Examples :
"We were unsure whether Mike would be up to the job, but in fact he has turned out to be an efficient and motivated worker."
"This market was thought to be heading for a slump but it has turned out to be quite resilient."
