the technological growth is expanding exponentially, so I think that by 50 years, quantum computing will be possible, and maybe even obsolete.
it took man thousands of years to make anything you could really call "technology"
in the next few thousand years, we gradually moved up the food chain and became civillised (to some degree)
and in the past 100-200 years, we've gone from being "medieval" to having computers, cars, aeroplanes, space travel, a lot of electrical appliances (TV, radio, lights etc..) , medical practice has advanced dramatically, we know heaps more about the universe and Physics (the world is not flat and is not the centre of the universe)
we've done all this in the past 100-200 years, and technology is still advancing at an increasing rate.
in a several thousand years, we went from basically nothing to relatively civillised, and have some knowledge of how things work
between 200 and 100 years ago, we about doubled or even quadrupled our technology (this is an estimate)
in the last 100 years, we've increased the technology by maybe a factor of at least 10
in the next century, we might increase out technology by, say a factor of about 20 to 40