This is getting complicated as Joomla 1.7 was released during autumn 2011, and VirtueMart 2.0 was to be released at roughly the same time, but it wasnt. As VirtueMart 1.1 wont work on Joomla 1.7, it looks as though my extensions will need to be upgraded to work on VirtueMart 2.0 and Joomla 1.7 in one swoop as there will be to many conflicting problems any other way. But from what it says on Virtuemarts download pages
"VirtueMart 1.1.9 is the latest stable version available. It is compatible with Joomla! 1.5.x only!"
http://virtuemart.net/downloads

But then of course, in January 2012, J2.5 will be released which has a life span of 18 months, so if i upgrade it to work on J1.7, a few weeks later i will need to upgrade it to J2.5.

You wont be able to upgrade your Joomla core system into J1.7, as VirtueMart 1.1 wont work with it, and VM2.0 isnt stable enough to use commercially yet and there will be database changes between RC1 and RC2 which could cause you a lot of issues of upgrading if you migrate now.

So what I have decided with all the sites I manage at the moment is that i will sit tight until Joomla 1.7 and VirtueMart 2.0 is released and i will prob release a V7.X of my Google Base extensions to fit with both of those versions of Joomla and VirtueMart.

So in basic terms here are the combinations

Joomla 1.5 and VirtueMart 1.1 - Works perfect together and are both stable

Joomla 1.5 and VirtueMart 2.0 - They work together, but VM2.0 is not stable yet
Joomla 1.7 and VirtueMart 2.0 - They will work together, but VM2.0 is not stable yet and they are building VM2.0 "stable release" to work with J1.7.
Joomla 1.7 and VirtueMart 1.1 - Do not work together

So as only J1.5 and 1.1 are stable, there is no way for me to release a version of my extension for anything other than these (yet), but as soon as these are released stable, we will release this to work on both.

I hope that makes sense ;)