Currently,if you do thing, after 10/1 your status will change to H1B. However if your new TN is appvoved, because the TN approval comes after H1B, your status will be changed back to TN. Getting a TN from border may have the similar effect. In order to get back to H1B (straight out your status), you have to cross the border again with H1B apporval notice and get your H1B back.