Talking about diversification, I'll rather diversify to another investment than investing in other Cryptocurrencies asides Bitcoin, at least one could still use some portion of the profits from other investments like Real Estate, Commodities to continue building their Bitcoin Portfolio.
If we check the performance of bitcoin over the last decade, you will notice that bitcoin is the most performing asset in terms of ROI. Bitcoin has given a better return than real estate or any other investment that you will think of. Sometimes when I hear people say that they want to take profit from their bitcoin investment and diversify to other investment it baffles me. Does it really make any sense that you are disposing the most performing asset to diversify to other things that can't give you half of what bitcoin will give you if you continue holding bitcoin.
I will rather stick with bitcoin than diversify to any other investment. As an investor if you think you have gotten enough bitcoin that's enough for you at the moment. It will be best to stack up cash, as diversification. with your bitcoin and cash deposit you are far better off than diversifying to real estate or anything else.