You could be. The lender can come back to you for the deficiency. Before you decide if foreclosure is the right step for you there maybe other options. For instance there is a Deed-in-lieu, Short sale then the foreclosure. Actually the lender could also pursue a deficiency in a Short Sale situation also. They may or may not do so.
There may also tax implications(with both a Foreclosure and a Short Sale) that you will need to discuss with a CPA.
There are so many things involved with a foreclosure. I would suggest you talking with a Realtor that deals with Short Sales in your area. They will know the benefit between going with a Short Sale vs a Foreclosure. And there are some benefits to going Short Sale than Foreclosure.
A Real Estate lawyer would be a great person to ask how long a bank has to come to you for the deficiency. The banks do have time lines that they have to follow.