We do not support switching in the middle of your term program to the subscription model. If your term has ended and you have not yet completed your graduation requirements, you can always purchase a subscription for that Nanodegree program. This may result in some changes to the content, and we cannot guarantee that your progress will be saved. If there were any passed projects in the previous version, you will still get credit for them.
If you have finished a Term 1 for a Nanodegree program and are ready for Term 2, you can either choose to enroll for Term 2 using a one-time payment for the advertised price at the time you enrolled, or move to one of the programs available in the subscription model. This may also result in some changes to the content, and we cannot guarantee that your progress will be saved.