It is no longer necessary to use this work-around, the WordPress Google Forms plugin now supports the new version of Google Forms. This post remains here are part of the development history of the plugin.
Thanks to a tip form Kevin Dillon, a work-around to the problem with new Google Forms has been identified! Legacy Google Forms are still available IF you start creating the form by opening a SpreadSheet first. Once the spreadsheet is open, select “Create a legacy Form” from the “Tools” menu. The form editor and published URL will be the same as those that had worked prior to the Google Forms update.