Rune translations:
Tablet:
THOSE
WHO SIT
ABOWE (ABOVE)
IN SHADOW
Is a reference to these rather obscure guys:
http://www.marvunapp.com/Appendix2/thosewhositthor.htm introduced first in X-Men/Alpha Flight by Chris Claremont back in '85, later used for the "final Raganarok" story that was Thor's 2004 "Avengers Disassembled" tie-in.
I'm not actually familiar with a tablet that would be connected to Those Who Sit Above In Shadow. Other than naming the group, I'm not sure what the significance of this as an artifact could be.
The text behind the Eternal Flame just says:
ETERNAL FLAME
Most puzzling: the text behind that "orb" says:
TUNING FORK
How that thing relates to a tuning fork, I have no idea. Note that the photos of the tablet and the Infinity Gauntlet were taken at the same alcove; you can make out the same patterns and "TUNING FORK" runes on the wall behind them. I suppose it's
possible that the text doesn't relate to the "orb" either, but I'd think someone on set would have been thinking about that.
Counting the tablet and its connection to the 2004 story, Surtur's Infinity Sword, and the Eternal Flame (which Surtur needs to light his sword and burn the Nine Realms,) that's three objects in that room that point to Ragnarok, definitely influenced by the version told in Walt Simonson's great
Thor run (which, I should note, was also where the Casket of Ancient Winters came from,) possibly influenced a bit by the more recent comics,
hopefully influenced by the awesome comics on this theme from Kirby. A film featuring all the forces of Asgard taking on a Godzilla-sized Surtur could be pretty fantastic.
They
might use the broken Bifrost as an excuse to confine this action to Asgard and all the realms other than Earth; the scale and stakes would otherwise logically demand the attention of SHEILD and the Avengers, in which case this would need to be the story of
Avengers 2, not
Thor 2. I think they probably don't want to have the team taking on Thor villains in every
Avengers movie.
If Ragnarok is
Thor 2, what could be
Thor 3? Where can you go after that, other than introducing Thanos (already hinted at by the Gauntlet) or another high-level cosmic threat?