The Upgrade Program doesn’t cause anything to happen to your older speakers. You can continue using them even after upgrading. Sonos support of those speakers doesn’t change regardless of whether or not you use the program.

However, that same device can not be used for another discount, either by you, or by anyone else who receives the speaker (if you sell it, for instance). The rebate is tied to the device ID, and gets “consumed”. 

Thanks for the response.