My Photo Stream discontinues-I already have additional storage. Do I need it?

Wondering about what’s going to happen come July 26.

See -> Information about the My Photo Stream shutdown

Information about the My Photo Stream shutdown – Apple Support (UK)

• My Photo Stream is scheduled to be shut down on 26 July 2023. 

• As part of this transition, new photo uploads to My Photo Stream from your devices will stop one month before, on 26 June 2023. Any photos uploaded to the service before that date will remain in iCloud for 30 days from the date of upload and will be available to any of your devices where My Photo Stream is currently enabled. By 26 July 2023, there will be no photos remaining in iCloud, and the service will be shut down. 

• Moving forward, iCloud Photos is the best way to keep the photos and videos you take up to date across all your devices and safely stored in iCloud. 

. . . and additional Google storage for $10/month. Do I need both?

You are the only one who can decide if you need both, it certainly depends on how many photos you have.

Enable iCloud Photos along with My Photo Stream so that your Photos from My Photo Stream are uploaded to iCloud automatically. If you already have then there is nothing to worry about. See the pic below

"My Photo Stream uploads your most recent photos (except Live Photos) so that you can view and import them to another device if you like. Photos are stored in My Photo Stream for 30 days and then are deleted from iCloud. To keep your photos stored in iCloud on an ongoing basis, set up and use iCloud Photos. iCloud Photos uploads all of your photos and videos to iCloud and keeps them up to date across your devices.

If you turn on both My Photo Stream and iCloud Photos on an iPhone, iPad, or iPod touch, photos that you take with that device upload to both iCloud Photos and My Photo Stream.

If you use another device with the same Apple ID that has only My Photo Stream turned on, photos that you take on that device upload only to My Photo Stream. They don't appear on any devices that have only iCloud Photos enabled."

Learn more about the differences between iCloud Photos and My Photo Stream.