"and based on the IRS info at the link above, it sounds like that if returns aren't e-file by 9am eastern time on October 19th, you won't be able to e-file again until 9am eastern time on November 2nd."

What I see at that page is that the Production System is Operational and that the Testing System will "be unavailable 9:00 a.m. Eastern time, October 19, 2020 until 9:00 a.m. Eastern time, November 2, 2020. The TY2020/PY2021 WSDLs, schemas and business rules will be loaded during this cutover. Please note: All existing test submissions will be deleted except for those sent in during the thirty days prior to cutover."

If you are not a testing entity, I don't see why you would be worried. If you are a testing entity, you should be glad that testing is beginning the cutover.