i am thinking what will happen when block halving reward will become negligible may be after 2050 or before that. even now itself miners had quit mining because profit dropped from 25 to 12.5 then think of 2050's situation.
That is a wrong statement. Before halving the exchange rates were around $230 per coin. So for every block, they were getting the equivalent of $5,750. And now, after the halving they are getting $740 per coin, for a total of $9,250. Actually their profits have increased by around 80%.
Historically that may be true, but as the reward continues to divide, I don't think that miners will continue to make the same amount. It would require the price of bitcoin to at least double every reward halving.
Past performance is not indicative of future results
it all hinges on adoption. for what bitcoin aims to be, internet money, it's currently a pitiful price. if it can't rise to accommodate more people and commerce then it's gonna be abandoned in lock step with the mining. it's a self perpetuating loop either towards success or death.
I don't particularly disagree with that, since it goes without saying that future adoption is what ultimately matters. Nevertheless, having said that, I still think that we are sort of insured from the necessity of doubling the price before or right after each halving. Let's assume that the price doesn't change at the next halving and halving itself doesn't get canceled. Obviously, miners will receive half as much revenue, and some of them may start leaving while others will continue mining since they all have different profit margins. But once some miners leave, the mining difficulty will decrease eventually, and the remaining miners will share the bitcoins that otherwise would be given to those who had left...
The inference is that, no matter how low the price might fall, mining will always be profitable in the long run