20% a year ago would have been a huge amount of new hardware, but 20% today?! I don't even know what to say, other than I do not see how the value of bitcoin and the halving can support this continued network growth.
When it comes down to it, after the halving, the continuing success of bitcoin is going to require one of the following two things (or a combination, I suppose) :
A. Sellers of bitcoin covering hard fiat costs (that's the mega miners/manufacturers) must become unwilling to sell their mined bitcoin at the current price, lowering supply
2. More non-miners must be willing to buy bitcoin on the open market, raising demand
Either way, the price of bitcoin must go up so the mega-miners will continue to do better than break even.
If neither of those things happen, then the miner-manufacturers will necessarily have to scale back their operations - at least to the extent that their bitcoin reserves can support them - just to keep from folding, and
the hashrate will drop (or, at minimum, flatline.) See: almost all of 2015 until the .25w asics were deployed at scale.
In short, the market will stabilize as it grows, so don't panic, think long term, and as always, don't play with your mortgage money.
This conversation happened before 4 years ago, and it will happen again 4 years from now. The difference today from 4 years ago is that we have some perspective from the first halving (the sheer panic of the unknown was palpable last time), and next time we'll have the perspective of two halvings to look back on.