Am I 'grandfathered' into the new 60-day visa status in Thailand after entering on a 30-day exemption?

Your current stamp should be good until June 8 so you will either have to visit immigration for a 30 day extension before then or leave the country. The new options have not yet come in to effect despite press speculation and we don't yet know when they will

The new 60 day rule has been approved , but it is not yet in force. Only after publication in the Royal Thai Gouvernment Gazette .

On 30 day visa excempt, you can extent 1 time 30 days in a Immigration office.

The DTV although not currently available is only something you would apply for prior to entering Thailand. If you are already in Thailand then it’s irrelevant if entry schemes become available or change.

There is no "grandfathering"

You entered Thailand and received the amount of days that you were supposed to receive according to the law. You'll be required to either leave Thailand or apply for the once per entry extension by the stamp in your passport. Nothing is ever done retroactively.

If you want a new stamp you leave and return and are subject to the laws in place at the moment you enter the country.