Change theme from Mesmerize

I have been thinking about what will happen with all my pages edited in the mesmerize editor. At the moment, when the theme is installed and active, the only way to actually edit the pages is in the editor. The text won′t show up in the regular wordpress editor.

If I change theme in the future, will all pages made in the theme editor be lost? or will they be editable in the regular wp-editor/Gutenberg?

/R