Are advances in technology making speakers better?

"Advances in technology always makes technical products better"

well.......

advances mean an improvement in one or many aspects. Which then have to be applied to the product in a way that it improves the product. Not trivial at all. 

The famous story is with the Ferrari F40: when the F50 came out, with better measurements in every aspect than the F40, it was still slower. Engineers spent months trying to figure out why. At the end they just conceded, sometimes awesome design is just hard to beat, it's not only about improvements.

Everybody’s different.  Some like to seek out the latest design/technology innovations in an attempt to stay or get ahead of the pack.  Others choose a well tested design and stick with it for years.  I started with a pair of used B & O BeoLab 8000 active speakers, which ceased production in 2010.  I added 12in and 15in sealed subs.  I’m pleased with the sound and look to my other components for upgrades.

Maybe I look at this differently. I never upgrade unless I can jump up another level. So if I found the very best for my budget… say fifteen years ago… I look for the very best I can buy at a minimum of 2x cost. This way what ever advances (yes, largely material science in speakers as @millercarbon says) occur are included with my purchase of a higher level product. I want my decision to result in a much better sound. It always does. 
 

I wouldn’t for instance buy brand x for $10k and ten years later buy the same brand x for whatever. Would it sound better? Yes… but the increment might not be worth it to my ears/brain… and that is what I am trying to satisfy. 

An advance that doesn’t make things better isn’t really much of an advance now is it?  

 Advances in technology != advance in sound 

it could be but doesn't have to be