Bitcoin, in my really humble opinion, will have others problems:
other the mentioned blockchain size and centralization that is coming, i fear that we are reaching the point of "not profitability". In 2020 each block will reward 6.25 bitcoin (now the reward is 25) and, except if price skyrocket again, i don't know if it will be still economically convenient to mine them, especially if we consider the increment of ASIC and hardware required.