I think that the billionaires do invest in bitcoins . Bitcoins has such huge market value and popularity , there is no way that they have not invested in bitcoins. If they don't invest bitcoins publicly , they invest in it privately . They prefer to remain silent.The billionaires has a lot of money , they can easily invest and profit out of it .
I am very much sure most of the billionaires must be aware of existences of such a new currency system and its potential too.
Who invest in Bitcoin and then tell everyone about it anyway? I think the only people that invest and tell everyone are those that are in multilevel marketing company. The only way for them to earn from that is to create a little hype by themselves. Things like bitcoin doesn't really need that. The hype is already there and you just have to ride with it. Another thing, if you have good money then you should always remain silent. Simply because otherwise people will think differently of you and treat you differently. They will always ask for a treat and even ask money from you. They will also ask for a loan from you. All of these are really unhealthy specially for someone who has a lot of money; he has a lot of things to manage.
I think that billionaires have multiple investments and they keep on looking for new things to invest on. So bitcoin should be known by them by now. It's been known for a couple of years now.