Hopefully you're right and that there will be/are services that make it fairly easy/cheap for anyone of any size to be compliant without a lot of extra work. While there are a lot of edge cases, the reality is that companies using a payment processor will probably be fine even though there's a mistake here and there--which no one will actually know about.

And the reality is that small businesses will mostly just fly under the radar if they want to even if some states don't have a floor for the sales that trigger taxes.