No… and yes. The sixth season of Lost introduced the concept of parallel worlds. In one world, Jack and Co. never crashed on the Island. In fact, in this world, the Island has been sunk. In the other world, all the castaways are now back on the Island in 2007 following a trippy time travel adventure. In this world, Juliet (Elizabeth Mitchell) is dead, having met her demise in the season premiere. Lost exec producers Carlton Cuse and Damon Lindelof hint that we may see Juliet again this season — presumably in the non-crash reality. (Missing Mitchell? Tune in to ABC’s V).
6x01 LA X - Elizabeth Mitchell - Juliet Burke - Lost - Sawyer - Season 6 - Season 6 Spoilers - Spoilers - Suliet