I don't remember seeing Pocket, so I went back to the settings to look. There's an option to have "Thought-provoking stories" which in smaller text says "Powered by Pocket".
Considering I didn't even realize it said Pocket the first time around, I think bookmarks are more prominent over Pocket, so I don't see bookmarks being demoted in favor of Pocket.
For a while, bookmarks were demoted in favor of Collections, a jankier version of bookmarks that didn't sync properly to desktop and included a button to open all of them at once in multiple tabs.
Collections are still there, but they've made it easier to use regular bookmarks too, so now Firefox for Android just has two versions of bookmarks in it for some reason.
Entirely unrelated to Pocket, as far as I know, except in the general sense of Mozilla having bad ideas related to bookmarks.
Considering I didn't even realize it said Pocket the first time around, I think bookmarks are more prominent over Pocket, so I don't see bookmarks being demoted in favor of Pocket.