An interesting theory has popped up over on Thai-based website zolkorn. They are speculating that AMD can only release 4-core and 8-core Ryzen models both with and without hyper-threading. This means that AMD will not release 6-core or even dual-core Ryzen processors.
They have explained their thoughts on this. Ryzen processors are built out of partitions that each have 4 physical cores in one module. Typical AMD processors had a dual-core setup, so if you wanted an 8-core or 6-core chip you would have 3 or 4 of these partitions active.
So now if AMD has a 4-core partition design that means that only 4-core or 8-core processors are possible. Now there could be the possibility that AMD can somehow laser cut two cores in a 4 core module to disable them, but that is just speculation at this point. But as of right now no 2 or 6-core modules have been mentioned from AMD.
One thing we do know is that we will for sure see four and eight core models.