I really like the look of the Game of Thrones and Cthulhu LCGs and would really like to get into playing these games, but I see that they've been going for a few years now and am a bit confused as to where to start. I notice that the core sets for both these games are out of stock. Are they not being made any more? Have they been replaced or are there new core sets coming out soon? Are these games actually out of print now, or are new sets still being made?

I think it is safe to assume that both core sets will be reprinted. Especially AGoT enjoys growing popularity, thanks to the TV show.

It's probably worthwhile to check game stores in your area (or even some online stores), as well. Often they still have them in stock.

Both games are still being produced and core sets are being reprinted.

Ah ok, in that case I'll see what's available locally, or maybe wait for the new printing. Do cards usually change between printings, or will it all be the same?

I think for AGoT reprinted versions have included errata. For CoC there's been no changes so far.