A very interesting article at Business Insider that worth reading: http://www.businessinsider.com/bitcoin-price-could-be-500000-by-2030-first-snapchat-investor-says-2017-3
I originally thought BTC might top out below $50k.
But now that I understand that BTC will be exclusively only the settlement layer for the mass scaling which will take place in altcoins, I now think his analysis may be correct.
All the power broker settlement will likely to be on the Bitcoin blockchain which will be the bulk of the fungible capital generated by the masses on the altcoins as dictated by the power-law (Zipf's law) distribution of wealth. Thus Bitcoin is the reserve currency of all the altcoins.
This is why one must stay invested in this sector. Note I do think the altcoins that scale up the masses will see faster appreciation than BTC in spurts, so that is one of way of increasing one's BTC if you are expert at speculation. Otherwise buy and hodl BTC.