Many people are stuck between liberal and conservtive. Why not be both? You can agree with social issues like homosexual marraige and drugs and believe in running the country's financial system like a conservative. For people who are sick of Democrats and Republicans the Libertarian Party is a great option.
The Libertarian party will continue to grow as time goes on. The reason for this is because the two party system draws a line down each issue and divides sides. A lot of people don't fit on the same side of every line. This allows the opportunity for another party to come in and grab some members. Currently is seems like the Libertarian party is poised to be that party.
I do not believe the Libertarian Party will grow in the future. The Libertarian Party was created in the 1970's and any upward mobility it had, has lost steam. There is no reason to believe that Libertarians will become vastly popular out of the blue. Since their platforms pick up from both sides (Democrats and Republicans) they'll remain stuck in the middle.