I am Canadian citizen & currently working on TN visa. My spouse is on J1 visa. I want to switch to J2 and get EAD. After couple of years he will apply for waiver and will move to H1. I believe I will be switched to H2 automatically as his dependant and my EAD will be void. Will that be possible at that time that I can switch back to my TN status?
You can switch back to TN. To correct slightly, you do not automatically get switched to an H-4 (not H-2).