As subject goes, is Bitcoin the maximum version?
Is it still possible to develop it?
or
Can we still expect better coin than Bitcoin?
Oh no of course.
There are bitcoins and there are altcoins, there is huge difference between them and altcoins were created in order to offer something better in it, some of them succeed this way. Let's talk about that, what bitcoin has and what it lacks.
Bitcoin is as simple as it is - it's decentralized, mineable with fixed supply, with some fees, with blockchain. Is it maximum? No, cause...
Bitcoin lacks anonymity and Monero rises here with it
Ring Signatures, it creates unique signatures and combine them with old ones, makes it hard to tell who created transaction and
Stealth addressing, making it hard to tell the destination of sent Monero.
Bitcoin lacks what Ethereum has - Smart Contracts and DApp platform.
Bitcoin Mining - It turned into commercial business.
There are still some currencies to compare bitcoin with, but I find it very boring and included example of two popular coins, Ethereum and Monero.
So to sum up, bitcoin isn't the current maximum version of cryptocurrencies.