Druvraj, I wrote a letter to the IRS (ITIN department) stating that wife has received SSN and that all her previous tax records be updated with the SSN in leiu of ITIN. ITIN is now not needed and can be rescinded.
IRS did send an acknowledgement letter stating that tax records were updated with SSN and that ITIN rescinded.
Here is a helpful link : http://www.immihelp.com/immigration/...tting-ssn.html