I have both versions, last year's and this year's (having just upgraded from the Air to the Air 2 and not yet resold my old iPad and cover). The covers are actually not identical. The band of fabric connecting the body of the cover to the magnetic strip along the edge looks to be roughly 1mm narrower on the newer model, about what you'd expect of a cover designed for a thinner iPad. The newer cover is also noticeably lighter than the old one, though the difference is small enough that this could be due to variances in manufacturing rather than intentional design.
That said, the old and new covers still fit the Air 2 more or less identically. I'd even say the old cover fits better, in that it lays completely flat against the screen, while the new one raises up slightly at the first fold. Which is to say, don't hesitate to get the old cover if you prefer, e.g., true black to dark grey.