Section 89A if become NRI in future years

I am currently a resident taxpayer with a foreign retirement account.  There is a good chance that I return back to USA after 4 years and again become NRI. 

In such a case, as per the rule 21AAA  all accrued income will be taxed in the year preceding the previous year.  Does this mean this will have an interest and penalty component? Do I need to amend the tax return? 

My main question is: If I have a good chance (not sure) of becoming NRI again (before withdrawal) should I still opt for 89A?