On November 4th 2014, the openSUSE Factory and openSUSE Tumbleweed rolling releases merged into a single openSUSE Tumbleweed rolling release.
Migrating to "new" Tumbleweed
Follow the "upgrade" procedure listed here: openSUSE:Tumbleweed_upgrade#Repositories
The above instructions will remove ALL additional repositories you have configured. You will need to re-add those you need.
Users who are using additional "openSUSE_Factory" repositories should be fine, besides the obvious "name mismatch" which is obviously cosmetic. The packages should still be suitable for the new Tumbleweed rolling release.