Just yesterday I've seen a bunch of canceled buy orders transformed into market orders. If this trend continues we will see drying up support pretty soon, right now people can still compensate by canceling sell orders so the overall order list looks the same.
Either way that are definitely the first signs of exhaustion.
I disagree with your conclusion. While buy orders may become market orders the graphs show no dramatic drop outside of the immediate buy events and have increased in general AND remain extraordinarily high. Today had the highest buy order depth EVER and even right now is equal to the high of yesterday.
Sadly I don't know of any chart which graphs the slope of the orderbook over time. This concerns the upper half of the buy orders and is reversed for the lower half. So while the size of the orderbook is increasing at the same immediate liquidity dries up.