I heard there was gonna be a GS3, but I can't find anything definite. Can anyone help me out? Am I really gonna be using my GS2 clear data, or do I have my hopes up for nothing?

This is what Wikipedia has to say (with references):

In regards to a sequel, a Camelot representative announced that "the current status of a third game ... is still up in the air", and Camelot's Hiroyuki and Shugo Takahashi stated in a 2004 interview that the scenarios of the first two games were intended as "prologues to the real event yet to come". Despite this, there have been no official announcements of a new Golden Sun title.

The lack of updates on any new releases following The Lost Age propagated several hoaxes. This included the unveiling of a Nintendo DS game called "Golden Sun: The Solar Soothsayer", which was reportedly shown off at a small pre-E3 2007 gathering. After this was decried as a hoax by official sources, the hoax's author confessed he made it in order to generate more discussion about the series and a sequel. The Takahashi brothers commented in October of 2007 that they still want to to make a third Golden Sun title, going so far as to say that they "have to" and that Nintendo themselves had asked them to make another. They claimed that they haven't thus far because they wish to give the title the development time it deserves.

Quote directly from the interview:

Hiroyuki Takahashi: First of all, I love that game and I love the world of Golden Sun. We think we have to make another one. We have to do it! Not just that we have to do it, but we want to do it. Nintendo has asked us to please make it. But at the same time we haven’t gotten around to making it. We’re not really sure why. (laughs)

October 2007 is pretty recent, but it doesn't seem like they've got any definite plans, or even a concept in development yet. *shrugs* Make of that what you will. I don't think there IS a definite yes or no on that question.

Well, that clears up the current hoax that I heard about for the DS. Thanks for helping me out. I really hope they make another one. I don't want to find out my clear data is useless.

I'd LOVE to see another Golden Sun...

It'd probably be on the DS though, and I don't have one. I guess if it's ever officially announced I'll have to spring for it.

I like golden sun, but I have yet to beat one, so I'm not sure what to do if they came out with a third one...

I absolutely loved the Golden Sun games. Still my favorite handheld RPG to this day. I beat the first and Lost Age.

I would be delighted to see another Golden Sun game release, but I'd want it to be with the same characters though. But what could you come up with after the events of Lost Age?

What they need to do is make a console version of the first two games.