I believe the limit for that version is 216 vEthernet Interfaces per VEM module, and 2048 per 1000v VDS. I think the 1024 limit is for the number of ports in a port group, but with multiple port groups you could exceed that limit on a per VDS basis.
The recently launched 2.2 version of the 1000v takes the scalability up to 300 per host and 4000 per VDS, but I'm not sure if the per port group changed.