How similar is this to the LLG version?

 Not being a huge board game guy, may I inquire as to what an LLG version is?

 the one you collect. 

 One would assume, by your most recent post, its similarity in terms of letters, and your top 5 that you are referring to the CoC LCG, in which case the answer is not at all.  It...well, it's sort of difficult to go into details, because there really are no notable similarities at all.  It's cooperative instead of competitive, there's only the base game, it's based on dice, you don't have a deck, etc.  Elder Sign is rather similar to Arkham, though.

My understanding of a LCG is that it's updated often with extra card packs and exspansions so that the game is constantly evolving.

Does this mean that elder signs will have no expansions packs?

 Most likely it won't have any on a regular basis. However there are small expansion cards for Death Angel in the POD section as well as another of their games which I don't recall off the top of my head. A new old one card was given out at the big event recently as well so I suspect there will be some sort of expansion support in the future just not every month like an lcg.