Definitely not a load of comets as NASA suggested and Michio Kaku also thinks that there is a possibility it might be alien megastructures. What he said is that 20% dimming is an unheard of amount of dimming in those viewing circumstances.
Basically, anything is possible as scientists have never had circumstances where this amount of dimming was seen in the past and they just have no idea what could cause it - so any hypothesis is on the table at the moment.... until they know it is definitely not a Dyson Sphere, then it is still possible according to some of the top scientists of today.
The Dyson Swarm. Of course aliens use this technology! There was talk of doing this to Planet Mercury. Blowing it up, scavenging the remains, and using the debris to harness solar energy...
