I'm sure it will become possible soon. The code is already there on iOS, as the app also work on iPad, but hidden behind the internal feature flag [0]. Same with Android [1]. If your second device in an Android, you can already use it now with [Molly](https://github.com/mollyim/mollyim-android).

Also, WhatsApp recently added this feature, so the expectations from potential new users who switched is now there.

[0] https://community.signalusers.org/t/allow-android-ios-device... [1] https://community.signalusers.org/t/allow-android-ios-device...