They talk about it with the same frequency that they talk about anything, which is, as you know, very little.
But I didn't only had the dev diaries and kickstarter videos, it was again pitched just before launch when the sale of expansion passes began (it was also the
main part of the newsletter article that promoted the LEPs). Later it was again stated by devs that it was on the roadmap. They don't talk about it "frequently" (at least in my definition of frequently), but FD doesn't exactly talk frequently about anything do they?
While it hasn't been written in blood under penalty of Braben losing it's soul to Satan, it was still stated several times in a manner that we can't trust them to their words, then we couldn't trust them with anything they say. After all, saying "look at all these amazing things we're going to add in the future, now buy expansion passes" and then dropping said stuff would be a huge bait and switch.
We finally agree!