One 1000v switch can only be joined to one Datacenter in vcenter.
Yes you can only have 64 hosts joined to a 1000v and each ESXi server can only be joined to one 1000v. Also you have the 2K~ port limit.
So to answer question as long as your pvdcs are coming out of the same vCenter Datacenter they could all be on the same 1000v.
Its not well documented but you can have more than one 1000v per vCenter Datacenter. This is useful if you need to scale past 64 hosts or you have different vlan requirements on different servers.