Hm,
I thought it took so long because I'm a fool. 
According to the documents vSphere Essentials Plus VSA is a vSphere 3 hosts bundle with VSA. And I checked the VSA key is included. But if I want a "new" host cluster with VSA I have to upgrade to vSphere full version instead of esentials.
Buit according to your answer we might talk about different products? VSA is virtual storage appliance and virtual san is a different product?
Sorry for my confusion