When it comes to the descendents, I'm sure there will be plenty of references to them like "*Sniffle* Oh, I'm sorry. It's just that...That was the staff your grandmother used" or something along those lines. And of course, if the world hasn't changed too drastically I hope to see a few possitive occurances that have stayed put from the first two games.
Until I know an official release date for this game, I'm not going to re-buy/pick up and play the first two games. Now I'm kicking myself for selling my Prima Strategy Guide for GS/TLA (I like knowing where all the hidden items were).
You remember how we sometimes had to battle Djinn in order to convince them to join the party? I sorta wish (you know, as some sort of mini-boss) we had to battle some of the bigger summons in order to get a Djinn. We sorta got that when it came to getting a few of those ancient tablets in TLA, but it's just an idea.
Now that we have the game, I hope they still keep the Blacksmith/Raw Matterial.
One more added plus: If you inserted your GSDS game and GS:TLA game into your DS and the GSDS game could transfer some of the information from TLA that would somewhat help you out in your journey. I mean, if these are supposed to be descendants of yours, don't you think they've left something behind? A weapon, a ring, a Lemurian Bone

, the Mars Star (please remind me, was that EVER used?), etc...
-BGS