Soken is just a workaholic, him not being around isn't a big thing. If you want to take everything into account he is the composer not the writer, director or producer, they usually aren't as public facing as he was so him not being around lately wasn't a big deal. Koji Fox was a case of he said he's moved over to XVI and his understudies were in charge of XIV while he was finishing up XVI...also he's a localisation person once again love the guy but he's not a face that would be connected to seeds of doubt of things going wrong.
The team is massive...compare what came in 5.1-5.3 to 6.1-6.3 its borderline tied or more in the 6.X favour (it just lacked enough rewards to bring longevity) I remember Yoshi P saying they shifted people back and forth to give new insight between XIV and XVI. It was good for the team to make something different because eventually, they become complacent. Think about it this way too...the visual upgrade is purely the work of XVI...a lot of the dev time and features shown in the screens are work done when making XVI...