If it were guaranteed that the price of bitcoin would stay the same as it is today, would you still buy it? My guess is, the answer is no. But if its value lies in being a currency, price stability is essential. And if your answer is no, how is it then not just a Ponzi scheme? In other words, everyone is buying it on the hope of someone paying more for it in the future, not to use it as a currency.
I would stop buying. If the price would not even go up, then bitcoins would not be a sustainable kind of invesment. With the price remaining at a stagnant state, no one would even invest or buy bitcoins anymore. I think some supporters would buy just because of its features alone this time around.