To throw a date on this: I did see Ironside and one his daughters at the TO studio last summer. This was just good timing, as I was there on other business.
I have two sources who worked on the set of The Space Between (
http://www.imdb.com/title/tt4682922/), which was shooting in TO. Ironside mentioned he was working on a new Splinter Cell. One source is someone I trust, the other is an acquaintance by degrees.
The movie shoot overlapped the same week as my encounter. As I understand it, he was here for the movie first and worked in the studio visit while in town.
None of us is bound by NDA over this, given our connections and circumstances, but it still feels shady to talk about since it's not official. I was surprised I hadn't seen this news from someone else by now, to be honest.
I know UbiSoft TO has a wonderful new mocap studio. While I did express disappointment it wasn't shown at E3, this thing could be early along. I haven't seen actual in-game assets or production assets for myself (like the Syndicate extra timeline story). I don't know who is making it. I know other dev studios have used the mocap studio.
Remember Ubisoft studios collaborate often. The TO studio contributed content to Watch_Dogs 2, and For Honor also takes up a chunk there. I'd like to say this was another TO take on the franchise, but I will not until I know more.