Thunderbolt 2 Won't be in the 2013 MBP
The first Intel chipsets with Thunderbolt 2 support will be released in the summer of 2014. The only way to get Thunderbolt 2 support before that will be with discrete Thunderbolt 2 chips, which is how the first generation Mac Pro will do it. There is no way Apple would use discrete Thunderbolt 2 chips in any product other than the Mac Pro, due to cost, when they get ordinary Thunderbolt support for free from the Intel chipset. There is simply not yet enough demand for Thunderbolt to justify it.
Intel will announce the availability of TB2 at IDF 2013 (September 10-12). Apple will release the MBPr w/TB2 the following week.
The first Intel chipsets with Thunderbolt 2 support will be released in the summer of 2014. The only way to get Thunderbolt 2 support before that will be with discrete Thunderbolt 2 chips, which is how the first generation Mac Pro will do it. There is no way Apple would use discrete Thunderbolt 2 chips in any product other than the Mac Pro, due to cost, when they get ordinary Thunderbolt support for free from the Intel chipset. There is simply not yet enough demand for Thunderbolt to justify it.