**The raven's words are never explicitly translated, but they are referenced later.**
In Chapter 6, "Hunted", of the same book _A Wizard of Earthsea_ :
> Hope and mistrust struggled in Ged’s mind as he listened. A wizardly man soon learns that few indeed of his meetings are chance ones, be they for good or for ill.
>
> "In what land is the Court of the Terrenon?"
>
> "In Osskill."
>
> At the sound of that name Ged saw for a moment, by a trick of memory, a black raven on green grass who looked up at him sidelong with an eye like polished stone, and spoke; but the words were forgotten.
>
> Google Books ref
Aside from that, I don't think we ever learn any more about the raven's words. Various fans have speculated, of course, just as you have. For example, this forum poster "figured it was a reference to the later trial at Terrenon with the spirit trapped in the stone", and this dictionary compiler listed the raven's phrase as "unknown; perhaps a warning about the Terrenon stone".