Above $300, plenty of gear will be profitable post-halving. And if it isn't... it will drop off, but not faster than what is corrected by the adjustment window. As mining gets less profitable, the cheaper way to acquire them becomes the market, which adjusts incentives accordingly.
I hope so. And people say things were OK last halving. But I think I noticed in the data that the block time did lengthen out for a while after it happened. I'll have to run the numbers.
The issue isn't obtaining bitcoins though, the issue is the lengthening of the block times and the corresponding drop on the transaction rate which may then cause the price to drop and make mining even more unprofitable which...