Although you will pass the substantial presence test and could be resident for the part of the year prior to moving out of the country, for the remainder of the year you will have a closer connection to the foreign country and so do not have to pay US income tax on the income for that period after you move.
"Closer Connection Exception to the Substantial Presence Test
Even if you passed the substantial presence test you can still be treated as a nonresident alien if you qualify for one of the following exceptions;
- The closer connection exception available to all aliens. Please refer to Conditions for a Closer Connection to a Foreign Country.
- The closer connection exception available only to students. Please refer to The Closer Connection Exception to the Substantial Presence Test for Foreign Students and Sample Letter."
It is accurate that you will file returns for a dual status alien for that year when your residence ends.
You can do as any other IRA account holder and either maintain the account or withdraw. If you withdraw there are penalties as well as including the income as subject to tax in the year withdrawn.
If you leave the funds to grow in the account when you do take out money as a nonresident will your IRA trustee would have to subtract "Non-resident Withholding" tax of 30% (unless there is a tax treaty between where you are resident when you withdraw and the United States that would enable you to claim a lower rate).
In most cases it will be better to let the IRA account grow tax deferred and withdraw later. There is no tax consequence until you withdraw from those accounts, regardless of where you reside.
For green card holders, your status will not change unless and until you get an official notice from the U.S. Citizenship and Immigration Service (USCIS) that there has been a final administrative or judicial determination that your green card has been revoked or abandoned.
When you surrender your green card during the taxable year, your tax status as a resident alien will terminate on the last day of that calendar year. However, if you can establish that, for the remainder of the calendar year, your home is in a foreign country or you maintain a closer connection to that foreign country than to the United States, your residency termination date will be the date you surrender your green card.
You may want to consider starting the surrender in 2013 instead of in 2014.
You are correct that you are not required to file Form 8854 as a long term resident.
"Before leaving the United States, all aliens (with certain exceptions) must obtain a certificate of compliance. This document, also popularly known as the sailing permit or departure permit, must be secured from the IRS before leaving the U.S. You will receive a sailing or departure permit after filing a Form 1040-C (PDF) or Form 2063 (PDF)."
Please ask if you need more discussion or clarification.