I think bitcoin has proved not to be a bubble since it's been around for more that one or two years. And of course, no, it is not too late to invest in it. However, you'd better be aware that the prospects and time frame for the market to get bullish are pretty uncertain and it is too hard to predict. It has been more a like matter of trust so far. So, it's totally up to you to decide whether or not to take a chance on it