Hello guys,

Major cryptocurrencies comes with many downsides such as large wallet size (over 190GB), huge cost for mining, etc.
What will be the future of cryptocurrency? If someone invents a new kind of digital currency that won't come with such downsides, what will happen to all existing cryptocurrencies?  or do you guys think cryptocurrencies will evolve and remove all of its problems?
I want to know what people will do when Bitcoin's wallet size reach 300GB or bigger.
And how long will it take to reach wallet size that people want to avoid downloading?