They upgraded "Pro" accounts to "Advanced" accounts without cost changes for ~1 year. After that you will have to pay $4.25 more per month for the "Standard" plan in order to keep MFA.
"To give you the most powerful admin control and security features, we’ve upgraded you to Advanced at no extra charge. You’ll keep your original pricing until January 6, 2018. After that, your account will adopt our new storage plans and pricing. If you want to downgrade to Standard, you’ll have until January 6, 2018 to do so."
"To give you the most powerful admin control and security features, we’ve upgraded you to Advanced at no extra charge. You’ll keep your original pricing until January 6, 2018. After that, your account will adopt our new storage plans and pricing. If you want to downgrade to Standard, you’ll have until January 6, 2018 to do so."