Stuff from 2012-2014 is no longer of much importance, but I'm not sure why folks (especially Donald himself) are so confused/misremembering here. I remember it well since there were periodic posts throughout the period, new people coming in and wondering if there was going to be another expansion and the best info being shared in response.
Essentially there was a stretch of around 3+ years, from before Guilds was released up until information on the upcoming Adventures expansion being worked on started to come out, that no one in the public had knowledge suggesting there would be another regular expansion, and the consensus based on Donald's many statements was essentially "there are no plans for one", i.e. probably not as far as we knew. Which is not to say plans can't change ("be made") and he couldn't decide to do more Dominion expansions one day. One day he did and et voila, Adventures.
Adventures was probably the most eagerly awaited release ever because, well, it had literally been 3 years since anything new of note had come out in the Dominion world. (Then we unfortunately had to wait even longer to actually play it online, because Isotropic had to shut down and Goko was soo bad).
So one remembers these things. It's not that Donald said there would "never" be an expansion, or even commented on the probability of there "eventually" being one. None of that is interesting. He wasn't working on one and there were no plans for one. That's all we knew, and really all we needed to know. Creators generally let you know once they're actively working on something that they hope to release in reasonable future to start pooling up demand; that's how it goes in any business and it's what happened here after ~3 years yo.