You asked what people expect if the app were changed. You addressed the question to me so I answered to be polite. I feel no panic or even concern. Your question was strange since it was pretty obvious what changes Apple might make to introduce Liquid Glass to Pages.
That's a very trivial usage of the app and that usage was how you framed your confusion about what Apple might change in Pages.
If you really were describing your own usage, then not much in Liquid Glass will effect you. It doesn't matter that the various controls used to manipulate the content might become harder to use, since you don't use them (or don't use them much).
Sorry I made the assumption that everyone already knew that. When I wrote "Apple positions Pages as part of an office suite" and "If they glass Pages, they will also have to glass Numbers and Keynote as well, to provide a coherent, unified design for the whole package.", I assumed everyone understood the suite consisted of Pages, Numbers, and Keynote. These are substitutes for Microsoft's Word, Excel, and Powerpoint, respectively.
Pages is a word processor/layout program. Numbers is a spreadsheet program. Keynote is a slide creation/presentation program. All of these application are document applications in that each window focuses on a single document identified in the title bar.