the google page creator is unlikely to break your site during an upgrade, as far as I can tell it's storing the text and images separately from the template even after page creation (like a CMS does). This means that even if they completely redesign the whole package, your content will be transferable.
Even if it weren't it wouldn't be hard to get the content out of it all.
Even if it weren't it wouldn't be hard to get the content out of it all.