If miners know (and they will know) that price is going up, before the halving they will try to not shell, so there will be a shortage of mined coins before the halving, triggering a rally.
Is this correct??
They will not know for sure if price would go up, maybe most of the people who want to buy before the reward halving have already bought long ago and after reward halving no one will buy
Mined coins only make up a small amount of the coins sold every day. If there's more demand it's possible more hoarded coins will become available. A rise is far from guaranteed just because there are fewer new coins arriving every day. If there's not enough demand then the supply becomes less relevant.
The demand can be very high or very low, but I guess it is on the higher end of the spectrum. This is very easy to tell due to asymmetric options in bitcoin investing: When you want to get large amount of bitcoins, you can mine; but when you want to get rid of large amount of coins, you can only sell
Mining is the lowest cost and have many other privacy benefits, serious demand will first seek their way into industry mining operation. This will have least impact on market, give them chance to accumulate large amount of bitcoin without raise the exchange rate
If the serious demand start to shrink, then the first thing we'll observe is that the difficulty will drop significantly. In fact, the difficulty has never dropped too much recent years, means the demand is still very strong: The hash rate keeps expanding means that investors not only invest in bitcoin, but also invest in infrastructure, have long term plan. Bitcoin is a virtual world's currency, in order to grow bitcoin, people have to grow this virtual world too, and mining is one of the important infrastructure
And after reward halving, when mining could not bring enough coins, hash rate might drop temporarily, and those investors will turn to market to purchase, and raise the price to a level that mining is profitable again