I'm just passing on info from my local Vredestein dealer who hasn't said that in so many words, but implied it and they only seem to stock the Cento. They can still get hold of sessanta but direct order from the factory in Holland (could just be how they prefer to hold stock)
The last time a situation like this happened with another manufacturer (can't remember who, sorry) the pattern that was direct order was shortly taken out of production.
It would seem a very silly business plan from Vredestein, as the Sessanta is building up a loyal following, but Vredestein has been taken over by the Indian tyre manufacturer Apollo Tyres within the last 8 months(ish) so a new owner might want to put their own mark on the brand?