A bank is unlikely to state they will not pursue a deficiency because that is a unilateral promise without consideration is therefore unenforceable. The bank cannot give the borrower an enforceable promise without consideration, i.e. something in return.
As to the income tax liability for the amount of the deficiency, the federal Mortgage Debt Forgiveness Act has been extended through 2013. This protects many short sellers from paying tax on the deficiency.... more