It sure feels like ICC->Cataclysm is the longest time ever between major content patches. And no ruby sanctum is not a major content patch. I'm not entirely sure when naxx40 was released in relation to the release of BC but I'm pretty sure it was less than a year. And before Wotlk we had sunwell and isle of quel'danas just a few months before.
And now if cataclysm comes in december it's a been a year since they released ICC. I'm sure this wasn't their plan and I kinda wonder why they got stuck with cataclysm development.