So the new Rebels trailer is out and after rewatching it 5 or so times I have come up with a pretty interesting theory. Throughout the trailer we see the rebels have new cruisers in their fleet, and these look almost exactly like the hammerhead cruisers from KOTOR 1+2. This shows they are drawing from KOTOR. Ahsoka even says in the beginning of the trailer that legends are based in truth, showing how they are bringing stuff back from legends material. So my theory is that the Sith looking temple that appears in the trailer is Malachor, a planet in KOTOR 2 that was important for your characters backstory. Malachor is ravaged by a super weapon, and lo and behold the visual dictionary for the force awakens mentions, "The Great Scourge of Malachor". I think they are the same because when Ezra has the cross guard lightsaber you can see the background is the same as that sith temple, and that stone statue looks like the victims of Pompei, so a victim of the Great Scourge perhaps? Also we get the mention of the Scourge in the visual dictionary in the section on Kylo Rens lightsaber, saying that it is based on an ancient design from the Great Scourge.
Tl:dr, Ezra is holding an ancient lightsaber on Malachor
OK, thats it, my nerdery couldn't contain itself and my brother who I discuss this stuff with is away at college, so to the internet it is!
:D