I do think that Nintendo should make a concerted effort to bring back or make new RPG franchises. Imagine if Nintendo's consistent exclusive RPGs included Golden Sun and Advance Wars alongside Fire Emblem and Xenoblade. But, from what I understand, the developers of Golden Sun just aren't currently interested (don't know if Nintendo own the IP or not).
I don't blame them since making Mario sports games is more efficient and brings in more revenue. A new Golden Sun game would probably take Camelot three years to produce and sell 1-2m if things go right while they could probably make two Mario Sports games in four years and get 5m+ in sales. Mario Tennis Aces alone might end up outselling the entire Golden Sun franchise.