- the weight of block-chain that can reach and go over 1TB (it start to become to big for a lot of users)
There were about 370,000 nodes in past, but now it's only about 5000 nodes because blockchain is big
In future, i think there'll less nodes, but all of them are very powerful
Also, we also need to raise block size too
- the computing power required to confirm every more and more transaction (not for all again)
Of course, more computing power will be needed in future.
But don't worry, mining technology is evolved quickly
- the probability that anyone can generate a private key from my public key
Just like generate a private key bitcoin address, almost impossible for now
- the probability that anyone generate a bruteforce attack generating a lot of keys (public,private) and steal bitcoin
It's called collision, but it's chance is very low, so it's not a thread