The actual IPS-version (which is 7.0(8) at the moment) supports IPv6 for traffic-inspection (it was added long time ago). But the IPS-Appliances and -modules don't support IPv6 for management. So your management-networks can't be IPv6 only.
It's hard to find official statements for IPv6-compliance, but it's mentioned on the data-sheet:
http://www.cisco.com/en/US/partner/prod/collateral/vpndevc/ps5729/ps5713/ps4077/ps9157/product_data_sheet09186a008014873c_ps4077_Products_Data_Sheet.html
You also find the corresponding Engines and signatures in the config-guide:
http://www.cisco.com/en/US/docs/security/ips/7.0/configuration/guide/idm/idmguide7.html
If you look at the signatures, you can see that there are a couple of IPv6-related signatures, but most of them are independent of the underlying transport.
