There are only really two things that can be upgraded on any MBP though - hard drive and RAM. Upgrading the SSD on the rMBP is incredibly simple (it just slides out and isn't soldered to the mother board as the inaccurate rumors have suggested). So that only really leaves RAM, which if you buy 16 Gig at purchase time, will be more than enough for the lifetime of the machine, unless you are something extreme like a motion picture editor or very high end 3D modeller, in which case you'd probably not be using a laptop anyway.