Yes, if the company petitions for one's permanent residence on the basis of an offer of permanent employment, the person will eventually get a green card. How long it will take depends on several factors: the type of job and the education and work experience required and the person's country of birth. The shortest period of time is about 1.5 years but it can take as long as 4-6 years if one is from China or India, for instance, and if one only has a bachelor's degree or equivalent.