You have two choices:

1. H-1B can directly transfer to TN even if you use up all 6 years. You may do that either by filing I-129 with USCIS or go to border to get new status.

2. Your wife can transfer to TD, but she has to get a visa stamp from U.S. consulate. TD can be issued to any citizenship, provides that he/she is a spouse of TN. You should get TN before she goes to apply TD.

3. TN can go directly to GC, if you qualify GC. H-1B => GC has some advantages, but not necessarily. Look the following threads for more:
http://web.wenxuecity.com/immigration/BBSView.php?SubID=ymmg&MsgID=33428