aptX HD will be available immediately, though of course you'll need aptX HD products in order to take advantage of the upgrade.
The codec builds on aptX's traditional claim of better than average Bluetooth audio quality, offering 24-bit HD audio support. There's no mention of whether it's 96kHz or 192kHz.
It will be backwards compatible with aptX, and we'd imagine the brands (more than 320 in total) that have delivered aptX phones and tablets, including HTC, LG, Samsung and Sony, will soon be on board.
aptX HD is immediately available - the CSR8675 Bluetooth platform is the one to look for, spec fans - so we will look out for the first compatible products.