Depends on what you define as microtransactions. When the value surges more the transaction fees may go down. For sure transactions on the level of the fees are wot worth to be executed.
This is exactly true, what is the definition of a microtransaction? Say Bitcoin is $40,000/coin in 5 years, is a .00001 BTC transaction still considered micro?
Probably not. The 5,430 sat limit isn't part of the protocol it is a rule enforced by nodes as an output that small is uneconomical. It would cost more in fee than the value of the output to spend. The min tx fee has declined over time, the dust threshold will also decline.