So, will mass adoption stabalize the prices of Bitcoin and altcoins?
Nothing will chance, crypto has been very volatile since its inception so I don't think that the price could be stable, perhaps it will be less volatile. Remember that the market is based on pure speculation so that eliminates stability to begin with.
When there's a fast changing fluctuations along with massive adoption there might be no stabilized price. Possible increasing price of bitcoin will happen same with other altcoins, it will definitely gain higher sustainable value. Although we seen that in a certain level right now, it seems stability was just a good start but eventually growth of each coins will happen randomly.