Since I don’t see a way to modify that information manually, I would recommend you either wait until Sonos produces one, or even contact Sonos Support directly to discuss it.

I usually suggest the phone folks, they have more tools available because they're on the phone with you, but they are available Monday through Friday during business hours. The Twitter support folks are available 24/7.

This change isn’t till May, I think there is time to see what happens  

I am in a similar position with three off CR100 controllers.

I called Sonos support about this and found out that they are woefully unprepared for the backlash.

First she told me that new products would continue to receive updates even with legacy units on my system. I read to her word for word how the Sonos website contradicts her. She admitted she knew very little about the details of the announcement. So it’s no surprise that I didn’t have much faith when she told me not to worry about old unused Bridge units that are showing up on my sonos.com Systems page effecting my system updates after May. 
 

When I explained I had a Play:5 and a Connect:Amp that I’d now have to pay big bucks to replace to continue updates on all my other speakers, she told me that since I had so many Sonos speakers that I should eliminate the legacy units or just rearrange my current fleet to cover the areas the old units are in. I’m sure the Sonos marketing folks would cringe hearing that.
 

The support team used to be a major selling point for Sonos. But now not so much. 

CR-100s aren’t legacy, they are current so it isn’t an issue here.

Yes that makes no sense but sign in and check it yourself.

https://www.sonos.com/myaccount/system/households/devices/