No update to the system that I can find anywhere so far. I'm pretty sure there was a system update in V18 or V19 though which brought it up to 1200. I could be wrong tho. I'd reckon seeing how V1 MMCS is now about 4-5 years old that there will be no further system updates and it'll continue as is for ever (unless someone hacks it and makes some changes ;-) )
To increase the volume for the Nav voice press the MENU button and the vol adj is at the very bottom of the page that shows up.