All accrued rewards from the past will be kept, and available through Play 4 Life.
You may need to select your instruments again after upgrading; this is to ensure you're able to modify your rewards throughout the term of your new membership plan.
Any rewards that are currently being earned on your plan will be upgraded to your new Play 4 Life rewards!
This means if you had Pro Play 4 Life 2020, and Upgraded to Play 4 Life 2021 - you would see 1 additional reward available, and on your next bill date (that is unchanged from before) you would renew your Play 4 Life 2021 membership and have additional rewards to choose.
This upgrade flow ensures all members are able to take advantage of the new promotion without disrupting previous rewards, or needing to pay to start a new membership regardless of how soon your next bill date is.