Not so with the NetBeans packager.
The NetBeans platform installer uses common code located in
{nbdir}\harness\nbi\stub
Customizing these files and sources allows you to brand you installer, which is all nice, but you would not expect to have to customize these files in order to get your program to upgrade.
Product version is controlled in two files, both which need to be changed.
product.version
in{nbdir}\harness\nbi\stub\ext\infra\build\products\helloworld\build.properties
version
attribute increate-bundle > component
in{nbdir}\harness\nbi\stub\build.xml
Stupid, but there you have it. Some day, when I have time, I'll try and automate it all.