It seems to me like as long as people keep trading in BTC they will go up and up
Yes, it seems like that to me also, but just remember: nothing in life is guaranteed. So many times I thought I knew of a "sure thing," only to be reminded of this lesson.
Bitcoin is only worth something as long as people are willing to buy it with real currency, but that only means it is worth something. That doesn't mean people will always be willing to pay more and more for it.
Who knows what will happen in the future. Maybe Litecoin will be seen as more valuable and BTC will disappear.
In the mean time, I'll see if I can't make some money in it and have some fun.