Not scalable for millions of users: Paypal can handle millions of transactions/day - Bitcoin cannot, and it would require revolutionary changes to the protocol to fix that problem
I have seen you make this claim several times before. I don't recall seeing your derivation thereof. Please show your work. The numerical assumptions that go into your proof will help to target the parts that need improvement.
My hypothesis is simple: bitcoin relies on a blockchain that is copied and evaluated by ALL nodes in the network.
All that want a copy of the blockchain, yes...
millions of users daily would mean that the blockchains grows to terrabytes in size,
Do you have an equation to justify this assertion? And even so, who cares? You can buy a 4TiB HDD today for about 0.333 XBT. Two years from now, the same _dollar_ cost will buy you 8TiB. Filesystems that scale to EiB are readily available. Who cares about storage?
and the nodes will need to allocate maybe 10% of that amount in RAM (more than 100 GB RAM).
This claim I am somewhat more skeptical of. Care to show your work? Even so, 16 GiB costs under one XBT today, and Moore's axoim shows no signs of stopping...
And each block itself has limits in how many transactions can be handled per block.
I am sure it does. What are those limits? Are these endemic to the protocol, or merely parameters used in the current clients?
The limit for bitcoin is 7 tps (transactions per second) compared to PayPals 100 tps or VISAs 8500 tps.
i was not aware of this number. Probably due to the fact that whatever it is, is enough for the time being. Where does this number come from? So we only need to increase the throughput 15x to match PayPal? Sounds like a trivial slam dunk to me.
I don't know whether or not it is true, but I read that Visa's all-time-high was 27,000 tps. Doesn't seem _that_ daunting. At least in light of the fact that we don't need that throughput before the network scales at last x4,000.
Bottlenecks for running bitcoin is: HDD, RAM, network speed. You could of course have several heavy datacenters around the world doing the work, but then we are back to a centralized system and the whole point of bitcoin being decentralized is lost.
As far as I care, I will consider it decentralized as long as there are no arbitrary barriers to anyone who wants to start up a full node. I do not consider dollar or time cost to be a valid consideration in 'is it decentralized?'
I believe this issue can be solved, but it should be handled before its to late, otherwise people will lose confidence in bitcoin.
I believe it will be solved. By the time it matters. If for no other reason, because the code base is open source, and there is plenty time for even li'l ol' me to learn the code well enough to make the necessary adjustments.