Members who continue to make payments without pausing until the park re-opens in the spring (or March 2 if the park is open year-round or if the park opens prior to March 2) will receive their free upgrades when the park re-opens in the spring (or March 1, whichever is later).
If you pause (or your Membership is paused) at any time between September 25 and the time the park re-opens in the spring (or March 1, whichever is later) you will not be eligible for a free upgrade.