It wouldn't be the first time that a new league team wins the champions title in the first year. In 1997, FC Kaiserslautern won the championsship after they played in the second league the year before. So Leipzig could repeat this success. I personally think that the team is too young (it is the youngest of all Bundesliga teams) to have the experience to win the season.
Yeah RB Leipzig just founded in 2009, but it doesnt mean they cant win Bundesliga title because of their young age. I am honestly also not sure they could get the title, but so far they have surprised us.