I've been, and still am speculating that Belarus will join the Russian Federation. However that includes Alexander Lukashenko being the next President when Putin steps down to sweeten that deal for Belarus, and that it will be done to allow the very rich to maintain their grip on power in Russia when they have to end their war and pull out of Ukraine. They've got to show some kind of win for Russia or they do face a citizen rebellion when Russia loses it's war with Ukraine.
And they will loose that war. So I'm not speculating that Belarus will join the war, rather they will be what allows Russia to loose the war without their very rich and powerful being killed by their own citizens during a bloody rebellion.
Putin in his speech praised Lukashenko much. To me that was seen as a furtherance of what I'm speculating about. That could be seen as a further setting of the stage for Lukashenko to make his entrance on the Russian stage with Belarus in his grip.