Do you think Ether will catch up? The technology is more advanced, but will scalability of ethereum be an issue?
Yes, bitcoin has a large number of users and they are very high as compared to ETH. ETH is also a potential currency but for now bitcoin is many years ahead of it and I think it will remain at the top of the list every time. Most of the cryptocurrency users trust bitcoin and used it in your every transaction as it is the best of all. The technology of bitcoin is a bit past technology but it has gained the interest of people and it value has reached at a very good height and is still increasing so I dont think that ETH will reach to the height of Bitcoin.
As you said bitcoin will be on the top of the crypto currency list because bitcoin is accepted world wide more than the ETH.Ethereum will be a good competitor for bitcoin in future but I don't think it will replace bitcoins.This is because ETH transactions are little bit complicated and the using ETH wallet also not easy for the common people.
But currently ETH is cheaper so it is better to grab our ETH now to make a huge profits in five years.