there are 2,100,000,000,000,000 units available and usable. and if anything happened and we needed more, for example because of an extremely large adoption, or a very large amount of coins lost or something like that we can still fork to a new chain which 0.1 satoshi becomes valid.
Or do we actually need more?
but as for your secondary kind of question, the cryptocurrency technology that bitcoin introduces is such a huge field to explore and innovate so we will never have enough. there will always going to be new cryptocurrencies being created and try new aspects and new ideas in this field.
- so many will fail
- so many will be copycats
- so many will not even be cryptocurrency, they will be pump and dumps
we may not see it happen today or for years in the future, but it is happening. there have been a lot of good improvements, the fact that they turned into ashes because of pump and dumps doesn't change the future.