Since the Pixel 5 has not even been announced, you will probably not receive any information.
But as already mentioned and also posted several times in the forum, Swisscom makes your data for VoLTE and WiFi calling available to all providers in the global GSMA database. We only know if the manufacturer integrates this or only in regional firmwares such as Samsung when someone tests it.
Since the Pixel devices were never officially sold by Goolge in Switzerland, the interest is probably rather small. But I read somewhere that it should work with the Pixel 4.
Google Pixel 5 - Wifi Calling und VoLTE