Watchtower does have a cash flow problem, but they are far from broke.
True, they can't sell buildings at profits forever, but they still have Assembly Halls and Kingdom Halls when they run out of Headquarters and branch buildings. They've taken the money away from congregations and they have cheapened their free offerings to the public and probably reduced the actual amount of printed materials going out.
It'll be a long haul. Eventually, the negative cash flow will catch up.