These type of monitoring is better suited by using netflow, as previous poster indicated currently none of the ASA models other than the 5580 supports netflow, and believe is in ASA roadmap in future.
http://www.cisco.com/en/US/docs/security/asa/asa81/release/notes/asarn81.html#wp229690
A workaround could be to use netflow on a router connecting behind asa firewall , or a router in front of your firewall, if you do decide to netflow on a router these two links have information on freeware or commertial collectors.
Commertial netflow collectors
http://www.cisco.com/warp/public/732/Tech/nmp/netflow/partners/commercial/index.shtml
Freee netflow collectors
http://www.cisco.com/warp/public/732/Tech/nmp/netflow/partners/freeware/index.shtml
As to when will next ASA release is, better is to check this link to see release notes, cisco does post this information on this link.
http://www.cisco.com/en/US/products/ps6120/prod_release_notes_list.html
Rgds
Jorge
Jorge Rodriguez
