Howto upgrade a process template from v3 to v4?

I am facing the same situation. Actually I will set up a 3.0.1. server, import the process template, upgrade and export again. To verify that process templates have changed between 3.0 and 4.0, you could "export" a standard template such as SCRUM by copy&pasting its process configuration XML and diff the two versions. I doubt that migrating the process template is as easy as replacing a version number in the XML. Wish it were, though.

well, there are new features in the 4.0 process XML, at least email templates..

so, I would guess (we still have to do this ourselves)

get the two base scrum template process sources, xmldiff, (3.0 and 4.0)

apply that dif (xmlpatch) to the v3 scrum source, to make sure you got the 4.0 source..

then dif your template against the 3.0 base to get ITS diff..

then apply your diff onto the 4.0 template.
and apply the 4.0 delta onto your custom 3.0 template,
and compare the two constructed 4.0+your stuff templates

Ok, finally i did a v3 install and upgraded from there. That was more a pragmatic decision. For the next major release it would be helpful to be able to upgrade process template via command line tool etc.