Its not listed in the patch notes, however I was flying around the Temple of Earth and noticed an instance portal. I zoned it out of curiosity and ended up in The Stonecore, the lvl 83ish dungeon in Deepholm. I was wondering is this supposed to happen, i.e. is The Stonecore avaliable for testing or should we stay away from it?

Yep, The Stonecore is open for testing. Feedback is always appreciated.