Ist bekannt was aus Erebor und den Zwergen nach dem letzten Teil von Der Hobbit geworden ist?

Nop

Wie fubar1871 gesagt hat: Dáin hat die Herrschaft übernommen, also gehörte der Goldberg nun ihm. Mit den Menschen, die ihre zerstörte Stadt Dale wieder aufbauten und mit den Zwergen im guten Einvernehmen standen.

In Bruchtal berichtet Gimli von den neuen Zuständen: “Nowhere are there any men so friendly to us as the Men of Dale. They are good folk, the Bardings. The grandson of Bard the Bowman rules them, Brand son of Bain son of Bard. He is a strong king, and his realm now reaches far south and east of Esgaroth.”

Und im Anhang stehen noch zwei Absätze über die Auswirkungen des Ringkrieges auf die Menschen und Zwerge der Region:

At the same time as the great armies besieged Minas Tirith a host of the allies of Sauron that had long threatened the borders of King Brand crossed the River Carnen, and Brand was driven back to Dale. There he had the aid of the Dwarves of Erebor; and there was a great battle at the Mountain's feet It lasted three days, but in the end both King Brand and King Dáin Ironfoot were slain, and the Easterlings had the victory. But they could not take the Gate. and many, both Dwarves and Men, took refuge in Erebor, and there withstood a siege.

When news came of the great victories in the South, then Sauron's northern army was filled with dismay; and the besieged came forth and routed them, and the remnant fled into the East and troubled Dale no more. Then Bard II, Brand's son, became King in Dale, and Thorin III Stonehelm, Dáin's son, became King under the Mountain. They sent their ambassadors to the crowning of King Elessar; and their realms remained ever after, as long as they lasted, in friendship with Gondor; and they were under the crown and protection of the King of the West.