I expect Canon will release one down the line, but first they'll release a 430EX II replacement with -RT, then wait for sales of both the 600EX-RT and it's new smaller cousin to slow down, before they release an RF receiver to allow older flashes to work with the RT system.
exactly my expectation. It would be so truly Canon to handle it that way.
* 600EX-RT is a 580EX II with radio wireless and 200m reflector added, but price nearly doubled
* ST-E3 lacks AF-light capability but is still bloody expensive
* Radio receivers enabling seemless radio control setups with new and existing Canon flashes being maliciously withheld ...
so incredibly wrong, so incredibly irksome, so incredibly short-sighted.
Radio receivers at a very reasonable price (think USD/Euro 99 !) would lead to really quick propagation of teh Canon wireless system in the market. It would still require purchase of at least an ST-E3 or one 600EX-RT ... and would make that purcase really worthwile. And if they like the radio-wireless experience, many users would sooner rather than later add additional 600EX-RT's (and other future radio-controlled flashes) to their setups.
Withholding simple receivers for 580 and 430 - at least for the version II's [if that is necessary to tie the entire setup into the camera menu system] and withholding firmware updates for pre-2012 bodies (5D 2, 7D) to also allow use of the mixed ETTL-manual "group" features on 600EX-RT/ST-E3 just makes a lot of people sit on the sidelines and wait to see whether Canon eventually gets its act together.
I for one, am holding off buying into the Canon radio-wireless system, until all components including receivers are out, prices have come down and a firmware update has finally enabled second curtain sync via the Canon wireless ETTL protocol and until my 7D gets a firmware upgrade that wil allow it to control radio-flashes exactly like 2012 EOS models (5D 3 and 1D X). If Canon charges outrageously I may pick up PWs or Phottix Odin to run my 580/II's and 430's radio-controlled. Until then I stick with optical control using the 7D's popup master-flash.