Yes, there was a time when LEGO did not have an ongoing Space theme on the argument that it would compete with the Star Wars theme (well, there was Life on Mars in there, but everyone seems to ignore that). I don't think they brought back Space because they had reached a certain point in the SW line, but just rather that they decided that the market would have enough demand for both Space and SW. More to the point, though, is 2001 and 2002. This is the gap between KK1 and KK2, when all we had were a couple of (albeit awesome) special sets rather than a general line. What was happening in 2001 and 2002? That's when they brought out the first two waves of Harry Potter, which is at least somewhat crossing with Castle. But then as the HP line continued (with another major offering in 2004, and again in 2011, and smaller offerings in the intervening years), Castle came out strong.
So is that a pattern? Or has the market changed in the last decade? If it is a pattern, it's possible that there will be very little Castle for a couple of years to open up market space for the Tolkien line, but then as the Tolkien theme continues, non-license Castle will come back in force. In the meantime, though, the pattern above is that we'll get some awesome special sets (e.g. Kingdoms Joust).
BTW, I'm not really sure what the objection is (aside from fleshies, but, c'mon, everyone here has access to the secondary market, and most people doing the objecting probably have hundreds of figs in their collection, so the complaint seems to be "I'm happy over here eating ice cream. It makes me mad that other people might eat pie.")
But aside from that, let's take this MOC:
"It's an inn!" say the Castle purists. "We love it!"
"It's my interpretation of the Prancing Pony" says Jon Furman (the builder).
"Arrgh! We hate it now! Down with Tolkien!" yell the Castle purists.
I mean, really? I suspect that a lot of the sets could be relabeled (and, I suppose, have non-fleshy figs swapped in), and all of us would be pretty excited by them.