I'm in Brazil for the next couple of years and apple products are way too expensive. I have a trip coming up and I'll be in Japan until the end of February. What are the chances of rMBP getting updated by then?
Exactly, don't expect a cpu/gpu update in the rMPB mid 2013's until mid 2014. By the time you're back - IF an early 2014 update occurs it'll be long past February.
It's possible but not likely that Apple make a minor update to the Haswell rMBPs as they did in February 2013 with the Ivy Bridge rMBPs. Things that might possibly change are DRAM capacity, SSD capacity, clock speed, and price.