It's too early to confirm that. A few Chinese leakers have posted list of devices that would receive Android 11 (unofficial). Given the fact that Xiaomi devices usually get two major Android updates since launch, it's safe to assume so. But we have to be wait until we get some official information from the devs. Plus, Mi MIX 3 5G isn't even updated to Android 10 eventhough it was part of Google's Android 10 beta program. So let's just keep patience and wait for Google to release Android 11 first. We may be getting some information in the coming months.

Cheers! :-)