We can still use bitcoin as investment place because it will be worth rather than we use it as payment system. Seems like altcoins are suitable to be use for payment system since there are a lot of stable coin. As we know stable coin is same with money fiat and everyone will be understood to be use it. I doubt with bitcoin it can be use as payment system by its user, because its price has been high and fee per transaction is really high also the metter of processing per transaction need a long time .
SegWit & Lightning are the answers on processing fee & speed, so, in the future there will be more and more improvements, so, it will be more comfortable to pay with
BTC