No. If you've been an active Setapp member for any time, your subscription terms and conditions, including price or the number of devices in your account, won't change and will stay the same as they were in your first payment.
Similarly, if you successfully resolve a billing issue during the grace period, the price and all other provisions of your plan will be the same as they were before the grace period.
New terms and prices only apply to new Setapp members. However, if you decide to change or reactivate your subscription (after canceling it or missing some subscription payments), the conditions may change. For example, you might be charged with a new, currently listed plan price — which might be different from the one you’d pay before termination.