The Play:5 is S1 only and the Sub Gen 4 is S2 only.  S1 will never be able to support S2 only devices.  

PS - Not a good idea to give your private email in a public forum.  It’s a recipe for Spam and scams.

No profile information to help us out here, really need to know if he has a Gen 1 or 2 Play 5.

True.  But since the poster asked “When will we be able to connect a sub 4 to play five speakers”, I assumed they couldn’t connect now and therefore the Play:5 is Gen 1.

Sub 4 is not compatible with Play:5 gen 1 or Gen 2:

Product compatibility

• Sub 4 is not compatible with Play:1, Play:3, Play:5 (Gen 2), Connect:Amp, SYMFONISK Bookshelf (Gen 1), or SYMFONISK Table lamp (Gen 1).
• All Sub products are not compatible with Move products, Roam products, ZP80, ZP90, Connect, or Connect:Amp (Gen 1).

App compatibility

• Sub 4 and Sub (Gen 3) are not compatible with the Sonos S1 Controller app.

Ahhh, I didn’t know that.  So my answer stands. It will never be possible.

I didn’t know it either so I looked it up before asking, I got a different answer here when checking the App version compatibility, which was the wrong question.

https://support.sonos.com/en-us/article/sonos-app-version-compatibility

This finds nothing:

https://support.sonos.com/en-us/search?q=Product+compatibility

Finally found that snippet here:

https://support.sonos.com/en-us/article/set-up-your-sonos-sub

The Sub 4 product guide has this but no mention of which are compatible or aren’t:

https://www.sonos.com/en-us/guides/sub

The play fives are gen 2 and for all that I have read I cannot get them to the sub 4.

As I said in an earlier post (copied from Sonos support page) “Sub 4 is not compatible with Play:1, Play:3, Play:5 (Gen 2)”.

Buy a Sub (Gen3) to use with the Play:5s