Sonos One and Sonos Five quite old now?

Hi.  I assume you mean the Play:5 gen 2?  The Sonos Five is the current model, launched two years ago. Sonos have pledged to support fully all speakers for at least five years after the model is discontinued, where ‘discontinued’ effectively means no longer on sale as the latest model on the Sonos website.  Even after full support has ended, the speakers are likely to be usable for several more years. The One is still on sale (although I guess one could argue gen 1 and gen 2 are different models).  The Play:5 gen 2 was discontinued two years ago.

There are many people still using Sonos ZP80s and ZP100s from circa 2005.

It’s quite easy anyway to change a Sonos speaker.

If you wait until you can no longer use your current speakers, I think you might be looking at the 2030s.  That certainly wouldn’t be hurrying.

Edit - ah, maybe you are wondering if you will get better features if you wait to purchase?  I think it will be a long wait before you get a significant enhancement to these models.  Sonos also have a good track record of adding features to existing speakers through software updates.  Obviously I have no knowledge of what Sonos may have just around the corner, so I can only give my opinion.

Buy and enjoy now.

I have no idea.  I doubt Sonos know that.  Putin may have blown us all up by then.  I have set out Sonos’ track record for avoiding complete obsolescence, which I think is unmatched in the tech sector. 

There is no Sonos Five gen 2.  The Sonos Five was launched in 2020, replacing the Play:5 gen 2.  

Note: I edited my post before seeing your latest post.

Edit: FWIW I have four Play:5 gen 2 bought at launch (I’ll take your word that was 2015, it sounds about right).  Still sounding great.  Sonos added Airplay 2 as a free upgrade when it was introduced a few years later (just an example)

The one thing that might be added to the Five as a gen 2 in the near future might be a microphone so that it can support Sonos Voice Control.  That is pure speculation on my part.

Sonos products hold their value really well so if you had to change the cost would not be great.

I’d advise buying now!

Your final question has been much debated with the clear conclusion that it's a matter of personal preference. 

I suggest you buy a pair of Ones and a Five direct from Sonos and try them out in your own home. You can return what you don't want. But you will probably keep them all!

I haven’t found any other system supported as long as Sonos promises, nothing close to what Sonos has actually done so far.

I can’t recall how old my original Sonos ZP gear is and it is still supported.