You will almost definitely get an OTA update, so my advice is do not even connect to WiFi before jailbreaking* and/or installing
Kindle_Touch_Hacking#Blocking_Official_Updates
It will probably be a good long time before Amazon actually starts shipping new PW2s with fw5.6.1, they certainly won't bother unpacking them all to update the firmware when it should get an OTA anyway. Most likely, Kindles ship with the latest firmware as of the day it was originally boxed up, which could be a while ago.
* -- the latest jailbreak reserves special root powers so it is safe to update... well, in the sense that KUAL and other infrastructure can handle root elevation through gandalf. It's still impossible to change your mind and decide you prefer older firmware, unless you like diags mode and a terminal shell. And know how to use disk destroy safely.