I did roughly expect that the Royal Edition content would be released over the course of a year after release. That's still possible if the flavor packs have a quicker turnaround time than ck2 dlcs did. But, Paradox did indeed never specify a timeframe for us. If it takes longer than a year, we'll just have to be patient and wait. (I'm not advocating for infinite patience - there is a point at which the timeframe for the Royal Edition content would become ridiculous.)
Regardless of the timeframe, I would like to repeat my plea for the devs to maintain some level of a presence here. Back at release, we knew they were collecting feedback and putting a patch together, and I was really glad to see that a couple of my threads bringing up specific issues were addressed in the patches (maybe not specifically because of me, but a man can dream

). We know that Paradox continues to address and overhaul aspects of the base game in free patches that come with dlcs, and I think there's still plenty of things to hash out to make the base game as good as it can be. But, I feel less inclined to post and debate issues when there's no indication that the devs are still actively involved.