I have a stereo that I purchased over 15 years ago(rechecked date), and it's kind of bulky but it sounds great to my ears. Is there any technological improvement that might make a new stereo better than this already 6 point surround sound (as far as how it sounds not whether it will receive bluetooth etc..)? Computers obviously are worth buying every 4 years but how can a sound be made better if a stereo is already reproducing the quality that it receives? What about speakers themselves, do newer speakers have improvements somehow that older ones didn't like CPU's having more transistors?
This is a very opinion-based question and likely to get closed by the adult-supervisors here. But meanwhile....
Has stereo equipment CHANGED in the last 10 years? Certainly. It is hard to find any area of technology that has not changed over time.
Has stereo equipment IMPROVED in the last 10 years? That is a different question. You could argue that switch-mode power amplifiers (Class-D or Class-T so-called by TriPath) Are practictically overtaking and replacing the old-style linear power amplifier designs. They are cheaper and more efficient, and can be made to perform just as good as linear designs (if maybe even better).
Some "retro" audio gear is experiencing a revival, like vinyl LP discs, etc. And you could argue that with modern technology we can make better black vinyl discs than back when they were the main media.
And some audio gear like reel-to-reel tape is also seeing minor revival interest in people who are fond of that particular kind of distortion.
OTOH there are some modern aspects of audio that seem to be regressing. Most people are listening to music that has been compressed with LOSSY compression (i.e. MP3) Few people anymore hear uncompressed music.
And more people are listening to music on cheap earbuds or lousy plastic toy "computer speakers".
Very few people care about Sound quality anymore. The wider population don't have critical ears and aren't aware of it. Many think beats headphones sound good despite evidence suggesting otherwise. If all people listen to is lossy music on crap gear how will they know any different. As for your 'stereo' it could only be improved if it is a 'seperates' system. Speakers don't improve over time in the same way some wood instruments do. They do change over time though and bed in. This is why it's crucial that if a speaker driver fails you must replace both drivers in each speaker cab not just the failed one.