I can't say if PayPal will cancel it. If it does, you will be informed and you can resubscribe. Since we give 20 grace period after the date till the account's paid for, you should have ample of time.
You can check your subscription status and the date till which the account's paid for in E-junkie Admin > Summary
If you want to change the payment source to be on the safe side, you can cancel the subscription from Admin and subscribe again and choose the payment source you want on the PayPal screen.