From what I have noticed, a lot of remakes have little of the original team aside from a producer or a scenario writer because remakes are mostly graphical updates with a few new scenarios added. The Final Fantasy IV DS update had one of the original scenario directors, but most of the material is there for them to work with. I'm sure if Square Enix wanted to contract Tetsuya Takahashi or Soraya Saga for a Xenogears remake that they could make that happen, so I would not completely discount the possibility, but I do think it is very unlikely.