I've the same question, and actually tried it yesterday. All add-ons and royalty stay. However, if you renew in the middle of a plan, you'll lost the remaining balance of the plan, unless you select to renew when the current plan ends.
Your welcome. I haven't checked out that section yet in my account but when you schedule a change plan on next renewal be sure to:
Clear your browser.
Reboot your device.
Open one tab only.
Use secret/incognito mode.
Chrome, Firefox, Microsoft Edge work best....safari apparently is having issues
If needed change your device.
If the price of your new plan is more than your old plan it is suggested that you manually top up your plan amount before renewal to avoid a possible autopay glitch that charges the cheaper plan to your card causing an "autopay" fail for insufficient funds and the account is suspended as a result.
