The answer from IBM was quite interesting.
First of all, we were assured that IBM Domino was not dead - far from it. It was alive, kicking and thriving.
It's no longer being considered "sexy" or "new" but is seen as a mature product which does exactly what it needs to do. IBM made it clear that they didn't intend to over-engineer notes by adding functionality simply so that they could bring a new version to the market.
IBM weren't subtle about it either, pointing the finger at Microsoft Word and asking "how many more features do you need in a word processor"? It was a good point, well made. After all, how much functionality did "the ruler" make to Microsoft Word - and was it worth the cost of the upgrade? In my experience, it's made a lot of things that I used to do much more difficult.
IBM does not want Notes and Domino to become "bloatware". In fact, they made it clear that many of their requests were for smaller clients, for example, to "make the firefox browser-based version of Notes available on iOS". Whether that actually happens is yet to be determined but it's clear that the future is "smaller".
There will be new versions of Notes as new requirements and fixes arise. Domino isn't going away but as it moves past the 25 years mark and loses it's sexy good looks, at least it has a plan to keep trim.