I notice that the core game is in stock, but that the three expansions are all "not available" does anyone know whether this means they've just run out for a while (i.e. awaiting reprints) or is this a product that's basically being discontinued.

Am I right in thinking that the FFG core game is compatabile with the 3 expansions listed here, but not with any of the older ones?

The three expansions were made for the older version of the game, and are not really compatible with the version FFG has available now.

The older release of the game (and the expansions) are out-of-print, and there are no plans to republish.

most likely a second edition will be coming like descent and game of thrones.

The currently available Silver Line Edition IS a second edition.  I think it unlikely that there will be a third edition.

It is my understanding that there are currently no expansions compatible with the silver line edition but that all the expansions are compatible with all editions other than the silverline.

Oliphant said:

That is correct. It's best to get the original version of the game - lots still for sale on ebay and BGG.

 are there any rule changes or differences between the original and the silverline editions?

Dr. Jeffrey Wills said:

I can only think of the Feature cards from Rivendell and Lothlorien in 2-player games. Originally, you'd deal 4 each and thus 4 were left undealt, while in Silverline I believe you deal out all 12 Feature cards even in 2-player. Not 100% on this, but that's my recollection of a brief look at the SL rules.

That's the only rule  change, an update really. I now use this new rule for the original game. The other changes made in the Silverline edition are in art, design, components and terms used in the rules for cards and components.

In my opinion the changes are for the worse and the worst is that the expansions (which are great and really add to the game) can't be used with the new Silverline edition.