Will cryptocurrencies be able to use for payment ?
Of course. You can do this here.
But, if you want to use it in your country, You should know whether your country allows cryptocurrency for payments.
Will it be useful and convenience ?
Yeah, this is very useful and very convenience. I have felt it myself, and this is very easy and helps me. You should try it and you will know for yourself that this is very helpful.
Which coin do you think the best for payment in the near future ?
Bitcoin.
Yeah I still choose Bitcoin.