Apple already bought Novauris so the Nuance licensing deal can be dropped sooner or later. Maybe Nuance is selling because they know the Apple's will drop its license with them.
In any case Nuance is not worth $6B+ to Apple because they have a ton of extra baggage that Apple does not need. Let Samsung buy them and then drop the licensing deal.
Samsung can have Nuance for $6B+
Microsoft and Google use their own technology, Apple will soon use its own as well.