why not both of them ? i think with saving 20-30% your profit/money to gold always be a good choice, they already have their own market that can'be ruined by any other thing, even bitcoin i think. Old people and traditional people that can't use technology still hard to believe bitcoin is really exist, but who knows ? we are the next generation of old people, we can teach the next generation 
I think a good idea by investing in both? Why not? If you have a lot of money you can share your money or the profits you get by investing in both. After all if the price of both goes up of course it can give double benefit to you rirght ?There is no doubt that bitcoin is a digital gold and people who are into bitcoins will prefer to hold their bitcoins for a long term as everyone knows that the price can reach to the moon in future which may never possible with gold as its very stable and couldn't go higher as bitcoins.