They said "you can change your billing cycle to a quarterly cycle in order to extend grandfathering beyond July 1st billing cycle" - so one additional quarter, if you prepay for that quarter, followed by the increased prices.
The only way you get current prices for another year is by prepaying by July 1.
Comments
They said later in the comments that it is possible to pay quarterly and still receive the grandfathering...
They said "you can change your billing cycle to a quarterly cycle in order to extend grandfathering beyond July 1st billing cycle" - so one additional quarter, if you prepay for that quarter, followed by the increased prices.
The only way you get current prices for another year is by prepaying by July 1.