It will take us more then a decade to mine 21M, so who knows.
More like a century but who is counting?
That's right, it will be over a century so then why do I keep seeing 2033 all over the place? I've seen reputable sites quote 2033 or something like that? Is it because the hashrate is always 2 weeks ahead and during those 2 weeks, due to a exponential climb in the hashrate and the difficulty lag, the reward scheme goes from 10 minutes to around 5 minutes and in theory that could even go under 1 minute for certain periods of time so people then may be guessing that the 21 million will in fact but totally mined in another 20 years?
First of all, if the block time goes down to 5 minutes instead of 10, that would imply that a 100% difficulty increase is needed. So far the highest we've had since the onset of the ASIC-age was the most recent one, 46%. So while block times are accelerated compared to the target of 10 minutes, it's not nearly that dramatic. And the general expectation is that the difficulty growth will slow down eventually, probably next year, and with it will come block times much closer to 10 minutes on average.
I'm not entirely sure why 2033 is coined as a year where all coins have been mined. It is factually wrong. What is true and relevant is that the speed at which coins are mined will decrease considerably over the next decade. With a block time of 10 minutes, there's a block reward halving every 4 years. At that rate, 2033 is the 6th block reward halving and at that point only 1/64th of all bitcoins are still left to be mined. With all the accelerated block times we've had, it's quite reasonable to assume that 2033 will actually be closer to the 7th block reward halving, which means that at that point more than 99% of all bitcoins will have been mined.
Block rewards will continue to be non-zero until they fall below 1 satoshi, which happens around the 32th block reward halving, which will take place 128 years after the Genesis Block (not counting speedup in block times). However the income from block rewards will be extremely low in the decades leading up to this moment, hopefully they'll be negligible compared to the transaction fees.