Bitcoin is whatever people miners say it is. Bitcoin has had hard forks but we still call it Bitcoin. And Bitcoin clearly will have more hard forks in the future.
If I count correctly there has only been one hardfork and it was merely a bugfix.
Really needed hashrate = The hashrate below which Bitcoin will be a victim of a >50% attack. We don't know what it is, but it still exists.
You're oversimplifying by forgetting the fact that someone with such hashpower has an incentive not to mess with Bitcoin.
But basically that's my point, there might be such a value (setting aside the added incentives), but it still makes no sense to talk about the network being "secure" or "insecure" since, as you said yourself, you have no idea and no way to know about the threshold.
Currently there is a limit of 1MB per block. Do you think this will remain forever?
I don't know, and the "lengthy" discussions are here to prove that a consensus is far from reached.
If so, good luck using your outdated version of Bitcoin that cannot scale above 3 transactions per second. (You can use off-chain payments and whatnot but 3 tx/s is still not enough).
Why would 3tx/s not be enough with most transactions being off-chain transactions and the chain only used for settlements between account hubs ?
I mean, if you're a miner you'd be tempted to use your voting power to not make too easy to get into a block.
You can speak like you know the future as much as you want, I won't join you.
What happens next isn't our call, it's the miners call.
The day it's harder to get all the pool operators on #bitcoin-dev at the same time you might see that pulling a hardfork might be much harder than what you think.