Hi Andrew, I do not know whether Python Apps team does any automatic migration of packages in SVN. Since I'm interested in gpxviewer (not as maintainer but as user) I'd volunteer to do the SVN to Git migration. From my perspective the Debian GIS team which also maintains several OSM related packages could be a better fit for gpxviewer than Python Apps.
What do you think: Should I do the migration and if yes, do you agree with the Debian GIS team? In any case you should create a login at salsa.debian.org and I would add you to the according project. Kind regards Andreas. -- http://fam-tille.de