What do you think, is it possible to have zero transaction costs for bitcoin/altcoin. At the moment there are many fees and are they justified and impossible to get around or is it possible to reduce or even remove them in the future?
Lightning Network fees are of magnitude of satoshis and even fractions of satoshi's. This is virtually zero-fee transactions. Because Lightning Network is built directly on top of Bitcoin's blockchain, it is theoretically just as secure as on-chain transactions (this is not the case now, because the project is still in beta and there might be bugs/vulnerabilities). All the altcoins that currently promise free transactions and huge scalability are insanely centralized, so I wouldn't even call them cryptocurrencies.