It's the other apps which use Siri that could make an upgrade desirable for me. I use Siri mostly for adding items to my Calendar, Reminders, Clock, etc. As long as they will still use basic Siri for those purposes, I won't need an upgrade. As far as using Siri through my watch to ask detailed questions which require AI, I will typically just use the iPhone or iPad.
I have a first gen AW SE which no longer can be used as a key for my Tesla, but my AW8 can be. If the AW8 starts to stumble for that task, I may have to upgrade. I blame Tesla for no longer supporting the older AW OS for that feature.
If either of my AW's quit providing the basic skills for which I bought them, like delivering notifications and texts to me, etc., I will be pissed. I expect them to maintain those features for many years to come.