season 4 I believe is about dharma, and we will see more of the numbers (The Valenzetti Equation: http://www.lostpedia.com/wiki/The_Valenzetti_Equation ) and the 4 toed statue.
Boring episode with cliffhanger at the end....they need to think up a new formula.....I love Lost...but come on...get to freaking Locke already....and I still have no answer to the 4 toed collosus foot
It was actually scheduled to go on for 8 seasons. I don't know if it equated to 100 episodes, but it wasn't supposed to be 4 seasons. Maybe they've put more episodes in each season than originally expected though.
They're most likely rankings as to the candidacy for the protector of the island. Note number 4 was Locke, the lowest number out of the losties (meaning the highest candidacy), he loved the island and was pretty much the perfect fit, then he died.