Samsung started to roll out JB 4.1.2 XXELKC for Galaxy S III GT-I9300, which contains several new features like multi view introduced in Galaxy Note 2, new gallery, new Samsung Keyboard with continous inputs support, etc


firmware details:
pda: XXELKC
modem: XXELKC
csc: OXXELK4
build date: 30 Nov 2012

some build info:
ro.build.id=JZO54K
ro.build.display.id=JZO54K.I9300XXELKC
ro.build.version.incremental=I9300XXELKC
ro.build.version.sdk=16
ro.build.version.codename=REL
ro.build.version.release=4.1.2
ro.build.date=Fri Nov 30 17:54:15 KST 2012
ro.build.description=m0xx-user 4.1.2 JZO54K I9300XXELKC release-keys
ro.build.fingerprint=samsung/m0xx/m0:4.1.2/JZO54K/I9300XXELKC:user/release-keys
ro.build.PDA=I9300XXELKC
ro.build.hidden_ver=I9300XXELKC
ro.build.changelist=566833

download links:
XXELKC - link 1 (by sammobile)