Currently I am working on OPT which is valid till Dec'09. My H1 has been approved this time. But my company may think of terminating my position very soon (before October 1st)

1. Will I get the validity of 3 years even if my H1 gets canceled before October 1st? Or somehow I need to convince my company to revoke H1 only after 10/01 to get that validity?
2. Will my OPT still continues till Dec'09 or I have to apply for Change of Status from H1 to OPT after losing job?
3. Given a condition that I get 3 years validity of H1, and I enroll for masters/PhD program for F1: Can I go back to H1 if I get another job next year? Can transfer my existing H1 to new employer that time? Or I have to apply again for H1 quota next year?

Thanks,