J'ai trouvé la réponse sur
http://amarok.kde.org/wiki/FAQ#Amarok_2.0_FAQ :
Will Amarok 2.0 be able to use my old collection? Will my tags, rating and statistic be lost?
-> One of our developers is working on a script to migrate all your old collection data to the Amarok 2.0 database. It will probably be ready for the Amarok 2.0 release.