I think there are a couple of people that could hold BTC for more than 3 years because the people I know who are into Bitcoins hold their btc's even more than 5 years and are still holding on to them up until now. So the answer would be a lot! Imagine how many people now are holding bitcoins, hopefully it will be enough for circulation too.
Yes, many people are holding bitcoins from a very long time with themselves. They are just waiting for their opportune moment, which havent arrived yet. I think they are doing right because patience is the most important step to work with.
I know it is hard but success without patience is not possible, you must have to be patient and thats exactly what the people are doing by holding their bitcoins.