I upgraded from a PLAYBAR to an Arc, and liked the difference. I still use PLAY:1s as surrounds, there’s no reason to upgrade your PLAY:3s, although a pair of Era 100 or Era 300s would be a nice upgrade, and you could use the PLAY:3s elsewhere. I use mine in my bedroom. Oh, haven’t upgraded my Sub from the original purpose, don’t see any need to. 

@Bushpilot

The Playbar is one of the oldest S2 ready products. But imho its sound still is very good. Some people also say „better“ than the Arc. 
If there‘s no need of Dolby Atmos for you I would stay with your current setup and keep it as long as possible. Maybe waiting for the next Sonos soundbar generation would make more sense. 
But in the end it’s your personal decision. 
I just can tell you that for me with DD5.1 and stereo content an Arc setup doesn’t sound better than your Playbar setup. 
Atmos of course kicks the Arc sound to another level if you will use such content. 

Thanks so much for your input.
I’ll probably just stick to my current system. 

Good call, IMHO. 
 

If you need to ask, there’s no new feature you’re looking for and you prob like the sound from your existing setup.