Word of God is great and we definitely rely on it a lot for this series, but if Nomura ever confirmed any pairing outside of the games, I wouldn’t bother listening to it. There are certain points where we have to believe in Death of the Author in order to enjoy a series both within its canon and outside of it, and I think shipping is one of those things that is very messy to discuss and touch for any creator. If they either don’t make it clear what characters are together or make a compelling argument within their canon as to why that pairing works, you open the series to a lot of discussion like this.
If SoKai was a more compelling and well-established pairing within the series with solid development, there wouldn’t be any doubt about where things stand. If we knew Nomura’s intentions about Namine and Riku, we wouldn’t even be discussing the potential of it based on that one scene at the end of 3. If Sora and Riku weren’t the most well-developed pair in the series, fans of it wouldn’t butt heads with others so often. Shipping would still happen, especially for us queer fans without pairings made for us, but it would be much less of a debate and more about the fun of shipping.