I’ve read and seen in some talks that Plasma can be implemented on Ethereum after Metropolis launches. What feature does Metropolis introduce that Plasma is going to require? I figure it is something to do with account abstraction, but I’m not certain the details.
Plasma could have been implemented on Frontier. The only reason it will take until after Metropolis launches is because Plasma implementations will take a while to actually write and test the code for.