They can't ban carry on entirely and survive. Too many people will refuse to fly under those conditions. Business travel would severely be crimped. If they do it, it will only be for a short while for the security theatre.

They *might* allow carry on, but forbid you from opening it, even to the point of obliging you to secure the latch with a plastic security tie or something. That would blow, but it would mean people could still carry their laptops, even if they couldn't use them.