30 million users?
My god, I have made a HUGE mistake (as I've said this in a few places). I've just re-read the wallpaper and my statement is completely wrong:
If we presume that a decentralized payment network exists and one person will make 3 blockchain transactions per year on average, Bitcoin will be able to support over 35 million users with 1MB blocks in ideal circumstances (assuming 2000 transactions per MB).
I must apologize. If anyone sees this mistake anywhere please notify me and I'll delete it.
I assume hardware is always getting better because HELLO! and libsecp256k1 offers 5x validation speeds.
Libsec256k1 does not have an effect on the validation problem (Gavin confirmed this somewhere on Reddit but I can't find it).
with the 1MB blocks currently all full, i seriously doubt thats true.
what happens when a payment channel with 10,000TX needs to be settled on the blockchain?
My statement is wrong (read above). However, the answer to your question is: It needs 1 transaction on-chain (to close the channel).