Well, let's not say the pattern isn't meaningful or imply that people are imagining the pattern is there. A year or so of these releases, barring Arcee, fit that pattern. It's a handful of engineered molds (Op, Sunstreaker, Bee/Cliff, and the Magnus armor, with Grimlock upcoming) but they've more or less kept to that.
That seems like a fair amount of data to extrapolate from. Now, if Ironhide marks a change in that pattern, that's well within Takara's remit, but that still means there was an older pattern to expand from.
That said, Hironori Kobayashi did say this (translated) in
this interview -- which does leave a lot of room for more.