The only way you could say an H1B is a path to immigration is for the case where a non-immigrant meets a spouse and get a green card through marriage. That's what happened to me, but this is really just by accident. Someone under a student visa could experience the same outcome for example.
You sait it yourself, the power of companies over H1Bs is overwhelming. Upon termination, an H1B has to leave the country in the following 24 hours, there is no "grace period" even though it's a widespread myth.