According to this accuracy could get down to ~1m (from the currect ~3m. Whether this will fully be available for all non-military uses is open to question. From what I've read on the Geocaching forum, to get this accuracy you'd also need new device(s) that can receive the additional signal that's generated.
TomTom 940 GO LIVE 9.401
Western_and_Central_Europe 885.4009
North_America 835.2419
Garmin Oregon 550 V5.50
120210-British-Isles+Contours-Routable-GMAPSUPP