The problem I perceived today is that if these massive mining farms have the intention of holding onto their mined coins, then they will only create a market with less liquidity and ultimately decrease the value of the coins they are holding.
I don't think there is a problem. Even if no more bitcoins are sold by miners, there are still around 1,200,000,000,000,000 satoshis available. That's more than 100 times the number of dollars in existence. It seems like an adequate supply.