I have completed 4.5 years of my H1B visa; my firm is starting my PERM-EB2 process currently.
I am planning to obtain 3 years of H1B extension with my I-140 approval (premium) before Dec 2011.

After I obtain those 3 years of H1B extension, can I convert to H4 (my spouse is on H1B) to finish a MBA at University of michigan and then utilize those 3 H1B years again with a new employer? My company will withdraw/revoke the I-140 once I tell them I am leaving but by that time I would have already obtained approval for 3 years of H1B extension.

Is it feasible?

Also do I get to retain my PD with my new employer after MBA.