I just found the following blurb on line (on Lost Pedia) on what we can expect to see happen on the current season of Lost:
*DON'T READ AHEAD IF YOU DON'T WANT ANY HINTS*
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"It has been hinted that there is no boat coming to the island;however, whoever is coming to the island is "a lot worse" than the Others. What happened between Ben and the real Henry Gale and how Ben was caught in Rousseau's trap on the survivors' fifty-eighth day will be explained. The four-toed statue will be addressed. Whether or not Kate is pregnant with a baby from Sawyer will be revealed in the first four episodes. What happened in the Hatch during its implosion will be explored. The fate of Sun and her unborn child will be made clear. What happened to Dr. Marvin Candle's arm will be addressed. How Libby wound up in the mental institution will be shown. What happened to Ben's childhood friend Annie will be revealed. More will be seen of the authoritative Other Jacob. Episodes will continue to feature flashbacks, in addition to flashforwards, which have revealed that Jack, Kate, Hurley, and Sayid escape the island; however, both Hurley and a depressed Jack believe it to be a mistake. Not all the survivors make it off the island. This season is apparently scarier and more violent than previous seasons. There will be more deaths, some of which take place in flashforwards. Time travel and other supernatural elements will be a part of the season, and decoy endings have been shot. In an interview with the Chicago Tribune, Damon Lindelof said that while "the show hasn’t entirely abandoned flashbacks...we’re done telling flashback stories that are not relevant to the uber-story of the island."

My response to this:
YAH we finally get to know more about how Libby ended up in the institution!