One thing you can be confident about is the writers' ability (or forced lack there-of) to stretch the show out finitely. There is a fixed end-date (end of season 6, supposedly), so pretty much every episode from here onward 'counts'. I'm sure they'll throw a few filler episodes in the middle of each season like they did in the past, but we're not just talking about your standard franchise where it has no defined limit. I give them some respect for setting some boundaries for themselves (for this initial series, anyhow).

There have been some holes and areas I found things lacking, especially the finale from season 4. They did this whole buildup about the Orchid station, and then went in, blew it up, and that was that. Think about how much time was spent finding out about the Swan, getting inside, figuring it out, etc in Season 2.

It looks like for Season 5, they will be filling in some of the backstories, adding in some of the future stories, and also adding in some of this "civil war" between the Others and the Dharma people.

Lots of unanswered questions still from the past seasons --

Where did the brand new (circa 2000's) washer and dryer prominently shown several times in the Swan station come from? No way that was on a pallet drop.

Is there really an infection?

Whatever happened with Dr. Candle / Chau / Wicklund / whatever his name is (shown from behind in season 5 premiere as being a family man)? When did his arm get crippled up (as seen in several (but not all) orientation videos later on)?

Who the fuck is Richard Alpert?