The PVDM3 modules that were released recently have 4x the capacity of the biggest PVDM2 chips. PVDM3-256 can do 256 G.711 calls and can do 64 people in a G.711 conference - versus 64 calls and 10 ppl in a conference max for the PVDM2-64. I think you can only use them in the new ISR g2 routers, though - because they are a larger form factor... the PVDM2 chips require an adapter to fit in the PVDM3 slots.
Cant wait to see if they will be able to do video conferencing on these new powerful chips!