30-year fixed or 5-year ARM?

[Peter Chan]

If my expectation of the interest rate is that it will be lower than what it is now by 2027-2028? 

Should I take advantage of the lower 5-year ARM rate now and hope to receive an even lower rate 5 years later?

Or take a 30-year and refinance 5 years later? 

I understand for either scenario to work, my assumption of the interest rate has to be correct.