This is exactly what people were saying when Bionicle ended. "If we don't get it back right now, we never will."
Well guess what, it came back, and it STILL didn't sell because it hadn't been gone long enough to actually miss it. If there's demand, there will be product. Why does there need to be an entire theme based around constraction for it to come back?
Also, @Square I've been saying Ninjago needs to end for 5 years now. Partially to annoy Meso, and partially because I never cared much for it