It's relevant to everyone - the amount of new supply is cut in half. This is what makes it deflationary.
Discussion
But I already know the total supply is approx 21M.
You can find all sorts of theories about liquidity impacts of miners selling/holding during certain parts of the cycle, which may have impacts on price in the short and medium term. As far as I’m concerned that’s all speculation and I think you are generally correct in the long term.