Can somebody fully explain to me what will happen if the limit of 21million bitcoins are all mined by miners? Does bitcoin die? Or volatility stop?
After all are mined, the miners will have to live with what they earn from transaction fees. That's all. (Edit: they get now too the block reward + the fees, after 21M the block reward will be 0 and I expect the fees to rise.)
Bitcoin should not die, because (especially after the changes in the right direction) the number of transactions should rise and the price of Bitcoin too (so even if they'd earn less bitcoin than now, they'll earn more $). At least this is the theory and the expectations.
The volatility is based on what the speculators do on the market. I expect the volatility get under control (maybe!) when Bitcoin will get properly regulated. And that's not related at all with the 21M magical number.