Heh . . . very nice topic. A lot of things to discuss here.
First, to get straight to the topic at hand. I'm pretty sure we'll see at least on more Gamecube game from Game Designers Studio. Remember, Yamauchi was the one who brokered the Square-Nintendo deal and his comments prior to the deal seem to indicate that he thought Square should develop 2-3 games for the Gamecube in return for GBA priveleges. I would be severely surprised if Yamauchi was the one who caved into Square's demands, rather than Square acquiescing to Yamacuhi's. Of course the Square - Enix merger may make that original deal moot, but still I think we'll see at least one more product. What will we see? If I could answer that, I would be taking over Louie the Cat's job. My best guess: A Secret of Mana Gamecube collaboration between Square and Brownie Brown. I think the GBA game is just setting the stage. Brownie Brown has expressed a desire to create a Gamecube game, but they may not have enough resources. Couple a Square supporting staff with Brownie Brown's talent, I can definitely see it happening.
On to Enix! The thing that people should note about Enix is that it really didn't/doesn't develop most of its games. Soul Blazer/Illusion of Gaia/Terrangima & Robotrek & ActRaiser were made by Quintet. As was noted earlier, Tri-Ace makes Star Ocean. Chun Soft makes Mysterious Dungeon. Heck, Level 5 is helping Enix with Dragon Warrior 8. To my knowledge, the Dragon Warrior series and The 7th Saga series are the only games that Enix directly developed. There may be a couple lesser known series that Enix did itself, but most of the Enix games you know and love were made by other developers. The point is, I'm not even sure if Enix can legally make sequels to some of the games you guys want to see sequels for. Most of the time the producer does hold the rights, but that's not always the case. Still, they definitely seem to be more interested in properties that they have had a greater hand in developing. That is the great thing that is touted about the Square-Enix merger: Enix's great production resources would be married with Square's vast development resources.
As for Terrangima, the reason it never came to the U.S. was because Enix shut down its North American office in the United States shortly before its scheduled arrival. They simply weren't gaining traction in the North American market. I think it was only two or three years ago that Enix finally reopened its North American branch. I remember that 1995 decision well and was extremely unhappy. Enix had a whole slew of games that I was interested in scheduled to come out in North America at the time: Dragon Warrior 6, 7th Saga II, Terrangima, Genesis, and I think there maybe was even one more. Anyway, I'm still baffled why Nintendo didn't pick up Terrangima when Enix dropped the ball, Nintendo had after all published Illusion of Gaia in the United States. Perhaps Gaia didn't do as well as anticipated.
As Mouse_Clicker pointed out, the man who had a hand in founding Quest and creating the Ogre Battle series, Yasumi Matsuno, does indeed have a negative attitude towards Nintendo. The reason that Ogre Battle and Tactics Ogre were made for the Super Nintedo is obvious, it was the RPG powerhouse in Japan at the time. But as Yuji Miyamoto asks, what about Ogre Battle 64? Matsuno was also in charge when Quest developed Final Fantasy Tactics. Well, funny thing, Matsuno left Quest and joined up with Square during the time period of Ogre Battle 64 and Tactics Ogre Advance's development. There's a lot of speculation that Matsuno was the one who had a hand in Square's decision to buy and absorb Quest. Matsuno is quite busy with Final Fantasy XII at the moment (he's the director), but it will be interesting to watch what happens with Ogre Battle in the future.
By the way, Yuji is right about unhappy Square directors, they've been bleeding talent for quite a while (see Monolith, Brownie Brown, Skip, and others). Square's deal with Nintendo was primarily about the GBA market, but a secondary objective was to stop some of that brain drain that had been going on at that company.
Well, I'm done with my treatise. ;-) If Bill would only reveal what he thinks he knows, I would be a happy man. Come on, we won't throw rotten vegetables at you if you happen to be wrong. ;-) Actually, I just caught that veiled hint at Super Mario RPG being the project. If that's what Nintendo and Square have up their sleeve, I would quite frankly bawl. SMRPG is quite possibly my least favorite Square game of all time. A well designed game, yes; enjoyable, somewhat, and coming from Square, that's just not good enough for me. I'll take Intelligent System's Paper Mario over Super Mario RPG any day.