No, Poser searches the runtimes that you tell it about for the files it needs to build your scene. As long as you add the runtime with your characters in it to the library in your new installation, it will be fine.

M4 and V4 themselves should still be installed to the main runtime, I believe - but your characters can be anywhere, so long as Poser is aware of their location(s).

Technical note: even if your scene file has an absolute path to the old program files location, which may happen if you had to locate files manually in the past, Poser will still search its attached runtimes.