I'd love plastic aspects and I reckon they probably are coming, but the image seems to depict a pretty substantial component, and you'd usually only see something that big on the base of a character model.
It is a unifying feature of newer Eldar characters across different ranges (the Yncarne, Eldrad Ulthran and the Harlequin characters all have this style of runic stone base) so it's almost certainly something Eldar-ey. Exodites? Ynnari? Phoenix Lords?