If you convert it to a 7/1 ARM then you are adding an adjustable rate feature that was not previously disclosed. This would be a refinancing under 1026.20 and would require new disclosures.
I agree, but also think the scenario Indy describes is probably a "refinancing", too. It's not cut & dried, but Section 1026.20(a), OI #3 says: "if a variable-rate feature was properly disclosed under the regulation, a rate change in accord with those disclosures is not a refinancing." We'll assume the original 5/1 was properly disclosed when the loan originated--but the change that's being considered now is NOT in accord with the original 5/1 disclosures. Additionally, the original loan was a 5/1 30-year loan and the modified loan would be a 5/1 25-year loan. If the deal is already done, I would argue (defensively) that a 5/1 is a 5/1. If you're still deciding what to do, however, I'd call this a "refinancing" out of an abundance of caution.