As we've seen, Thano's domain (sanctuary) is a mere pile of floating rocks and destroyed planets. As seen in the mid-credit scene of Avengers: Age of Ultron, he is in a pretty fancy place taking the Infinity Gauntlet.
Now where did we previously see the Infinity Gauntlet? Oh that's right! Asgard!
After the break-in's, don't you think Odin would have put the Gauntlet in maximum security? And now that Loki's in control of the place, Thanos can just walk right in the front door. All his subjects have failed him so why not step into do his own dirty-work (beside he'll probably get Death's attention. With Infinity Wars coming in 2017 we have a lot to expect. Loki might even be dead! You've seen Thanos' warnings towards Ronan, why give Loki a second chance? Just walk into the Asgard palace and murder the dumb god.
Tell me what you think. (sorry this is really short)