Is it possible that the coin's value will go down or no?
Unfortunately we don't know what the future holds.
Everybody knows that cryptocurrencies are very volatile assets and you can get burned. There are many miners that don't take the risk and convert their earnings to USD as soon as they can.
But if you think that many have sold Bitcoin at 200$ or sold Monero at under 1$, if you look back they've made a bad choice.