You might have heard the news about the star KIC 8462852, 1480 light years away from Earth. It has been dimming up to 22% in a totally irregular pattern. At first, astronomers suspected comets to be the culprit. When this theory didn’t seem very likely, the more far-out hypothesis that aliens might be building a Dyson sphere around that star has been put forward.
There hasn’t been any additional evidence for the presence for a Dyson sphere beyond the irregular dimming. However, a recent finding makes the comet theory really unlikely:
The star has actually been dimming by 20% between 1890 and 1980! That would require a unrealistic whole lot of highly irregular comets. So, the Dyson sphere hypothesis becomes relatively plausible again. Now, the scientist claims that aliens can’t build such a big fraction of a Dyson sphere within a century. But, as most people, he’s probably not a futurist, so he probably has no idea what advanced nanotechnology and artificial intelligence may be capable of. I think it’s quite plausible that aliens might build about 20% of a Dyson sphere within a single century.
Futurist Georgy Dvorsky has more expertise on estimating such possibilities. He thinks that we could build a Dyson sphere within about half a century, once we have the necessary technologies for doing that, which we might have in 25 to 50 years. His scenario was criticised, and it was pointed out that it would probably take more like 2 centuries to build a Dyson sphere.
Let’s just assume that the aliens are superintelligent and are indeed able to build a (significant fraction of a) Dyson sphere within a single century by applying special tricks that the authors above haven’t considered. What we get is an eerily plausible scenario in which the alien civilization around KIC 8462852 has indeed used very intelligent tricks and highly advanced technology to create a large fraction of a Dyson sphere within about a century.
If that is indeed true, it might a reason for optimism: When there’s an advanced alien civilization relatively close to our home, then it looks like it’s quite possible to reach that stage of development without blowing ourselves up! phew 
Also, we might get visitors soon, if those aliens got serious about expanding into the cosmos (the alternative would be a scenario in which they got locked in to their own solar system for any number of reasons and decided to ignore the rest of the galaxy). Perhaps they are already here, but aren’t showing themselves very openly.
However, there’s a plausibility problem with that optimistic scenario. Why haven’t we seen signs for Dyson spheres in the rest of the universe? Shouldn’t the universe be full of Dyson spheres, if it’s easy to get to that stage? Well, if alien civilization stayed at that stage of technological development, then yes. On the other hand, If we accept the possibility that there are technologies that are so incomprehensively advanced that they make look Dyson spheres look like primitive stone tools by comparison, then we should indeed not assume to see a universe full of Dyson spheres. In fact, we only should expect to see Dyson spheres around the time that they actually fit the transient technological development level at which their construction is possible and looks like a good idea! When aliens progress beyond to “trans-Dyson-technologies”, we should expect that only few Dyson-spheres remain as museum-like artefacts, if at all.
So, this finding, if it is to be trusted is indeed very interesting. Not only would it show that we can expect to build a Dyson sphere within few centuries, but also that there’s even a technological state beyond Dyson-sphere-technology, which makes building them redundant.
As conclusion, we should expect to live in a cosmos that is full of trans-Dyson civilizations. Apparently they are very good at following the equivalent of the Prime Directive:
Most likely, they have good reasons for not overtly contacting us, otherwise it should be no problem for them to do that (in a way that we would understand). And the implications of these good reasons existing is … very interesting in itself.
But then, I might have created the equivalent of the geocentric model involving lots of epicycles here. By stacking a lot of unconfirmed hypothesis one upon the other, I arrived at something that could be called a plausible and consistent model, but reality could very well be much simpler – or even much more complicated than any of us could have imagined.