If bitcoin became a legal currency, many people will notice bitcoin and start using bitcoins. It will give a good impact into bitcoin for sure and the price of bitcoin can increase.
More and more people will start using it, yes. But a "good impact" may not be a good way to put it because we can't know for sure if being popular is beneficial to the bitcoin industry.
Being popular is for sure beneficial for bitcoin industry as popularity brings investments and investments decides if where bitcoin will go, the more its demand increases the more its price will increase as well, suppose you have 1 bitcoin and there are 5 people willing to buy it, wont they try to win it by bidding higher? That would be the case with bitcoin if it gets more popular.