Question about Companion supplements
 

Are these meant to be eventually subsumed into Campaign Settings or should I just go on and buy them? I really don't want to pick up anything that will be superceded.

At a guess I'd say no! The rate that Paizo throws supplements out through various product lines is phenomenal and, I presume, a successful business model.

I'd hazard an opinion that the current format of "Player Companion", "Adventure Path", "Module", "Campaign Setting" and "Roleplaying Game" lines will continue for the foreseeable future and Lone Wolf will bundle the requisite packages together. The fact that Inner Sea World Guide was released as part of the core data was inspired and an indication of the commitment of all parties involved.

Presumably any changes to the existing data would be iteratively updated to match the current errata.

IMO!:)