Hello,
Here's a quote from the ISRG2 Q&A document:
http://www.cisco.com/en/US/partner/prod/collateral/routers/ps10538/qa_c67_553891.html
Q. What module will replace the Cisco AIM-VPN Module?
A. There is currently no plan for any VPN acceleration ISM module. The integrated services routers generation 2 include built-in hardware acceleration for encrypted traffic, and in effect they already include AIM-VPN functions as part of the default platform hardware.
Hope this answers your question!
-Joe