I wouldn't say rock solid, I'm sure if you look at their books they have been bleeding money for decades with their cost of manufacturing printed material that hardly nobody wants to read, so much so that they required pledges from their members and basically stolen all their congregations cash on hand in excess of a few month operating cost, plus they put a hold on all construction project accept 2 or three(big money drain) and are selling all the tools they have for construction at discount prices.
Or that's what they are lead to believe. Look at how many KHs were given to them for free, and how many they have sold. That alone, without counting on their Brooklyn prime real estate, along with continuing having free labor, nope, they are just fine.
However, to be honest, I personally don't care one way or another. They can prosper or they can go bankrupt. Either way they are out of my life. I don't need to see them suffer for me to feel ok.