Yup. Xenoblade is more important than some people realize. It is Nintendo basically taking an IP which got good (BUT not GREAT) response and trying to expand it further. They are trying to take it from a one-shot wonder (small) to a big franchise. We can easily see that with the inclusion of Shulk, Xenoblade on New 3DS and Xenoblade Chronicles X on Wii U. Nintendo is pushing Xenoblade hard and its success will help fans of other small franchises as well, not just GS.
GS and Xenoblade are poles apart in the way they play except that both are JRPGs and both are small-mid sized IPs. Xenoblade's success will definitely make Nintendo consider other franchises to be bumped up. Plus it will also help us to get more JRPGs on the Wii U if XCX sells a lot.
It might be a bit unfortunate that GS is not getting the same treatment but the success of XCX can easily act as a catalyst for the former. It is not like they are going to make XCX2 right after XCX comes out of the gate. Seeing the success of an inhouse JRPG will definitely make them consider their other franchises to add more JRPG variety on their consoles. As you said, they have to be convinced that Camelot would be better off working with a Nintendo Dev team on Golden Sun instead of making yet another Mario Golf or Mario Tennis. Hopefully they have already anticipated this and started work on GS4 instead of waiting for the Wii U game to make an impact.
As a side bonus, the success of Xenoblade X might make some of the other JRPG 3rd parties consider the Wii U again after they have mostly shifted to the Playstation.
Disclaimer:
I am also a big fan of Xenoblade but GS first
Yea sadly so far, FE looks like it is continuously being favoured compared to Advance Wars (which I find superior in many aspects).
Heck if Golden Sun: Dark Dawn was a 3DS launch title (or a title when the 3DS was picking up steam) instead of a tail-end title on DS, this scenario wouldn't be occurring. Dark Dawn was released just 3 months before the 3DS launched in Japan. Considering Nintendo games are evergreen, it would be getting a lot more attention than it is now due to its bad timing.