If I understand the numbers - it looks like you are paying $40,000 a year in mortgage interest equaling $3333/ month in mtg interest. Depending on your tax bracket [lets call it 33% for the illustration] your net cost of interest is $2222 per month.
If you down size, what would your payment be then? Determine the interest you would be paying, slice 1/3 of it off [or actual tax bracket]. Subtract the new number from $2222.
That [not taking equity/ principle pay down into account] amount of $2222 - "x" would equal your real savings. After you establish that amount, you will have a better gauge on the actual comparison you should be making.
If there is nothing holding you in the house on a personal level - then you need to balance the 40-80k with the loss you would take today. I am not a Realtor, but as a CMPS Mortgage Planner, I can introduce you to someone that can help quantify those decisions.
This sounds more like a strategy dependent question than, "Should I sell my house". Time to get good solid advice.
Orlando Mortgage Pro [dot] com
Have you received a CMA or Appraisal on your house to see what it may sell for today? Have you done your research on what may happen in the future in regards to home prices? What is your time frame for how long you would be willing to hold onto the property?
If it's only two years, Depending on the location of the home there is a very high chance the home will be worth at most the same as it does today (not likely appreciation in the next couple years) and a decent chance it could be worth less.
I'd be happy to go over the numbers with you, and if you happen to be underwater discuss the options you have alond with each of their ramifications.
Your question is similar to a lot of homeowners. If you are interested, please directly contact me with your information regarding your property and we can discuss alternatives for you, your home's present value if you chose to sell and any positive or negative ramifications of a particular course of action.
I work with numerous sellers in various types of situations and would be glad to help. I can be reached either via cell at 407-595-9700 or E-mail to email@example.com.
Keller Williams Mega Agent