It is just good to think about it for a moment and the possibility of it being true.
There are more technical reasons, why I think it is unlikely:
You have one piece of work. If you solve it, it will solve a block from both Bitcoin and BitDNS. In concept, they're tied together by a Merkle Tree. To hand it in to Bitcoin, you break off the BitDNS branch, and to hand it in to BitDNS, you break off the Bitcoin branch.
Again: read it sentence by sentence, word by word. And tell me: where you can see this implementation in NameCoin? Do you have any "merkle root of all chains" anywhere? Can you see the accumulated Proof of Work for SHA-256, and go into different chains, by reaching different leaves in the "global superchain merkle tree"? NameCoin didn't even try to implement things in that way, and first copy-pasted Bitcoin's code, and then forked into a version with Merged Mining, which was completely incompatible with Satoshi's description.
In practice, to retrofit it for Bitcoin, the BitDNS side would have to have maybe ~200 extra bytes, but that's not a big deal. You've been talking about 50 domains per block, which would dwarf that little 200 bytes per block for backward compatibility. We could potentially schedule a far in future block when Bitcoin would upgrade to a modernised arrangement with the Merkle Tree on top, if we care enough about saving a few bytes.
See? At that point in time, Satoshi even thought about potential Bitcoin network upgrade, where instead of what you have today, you would have that "superchain merkle root" available by default! And not only NameCoin's design was not superior enough, to convince Bitcoin developers to upgrade into "multichain code", but instead, it discouraged people from trying Merged Mining, when they saw, that NameCoin can be 51% attacked, without harming Bitcoin's chain, because different networks had different difficulties! And since then, altcoins started to switch from SHA-256 into different hash functions, because they couldn't implement Merged Mining correctly, and had no other ideas, how to prevent their alternative chains from attacks.
Note that the chains are below this new Merkle Tree. That is, each of Bitcoin and BitDNS have their own chain links inside their blocks. This is inverted from the common timestamp server arrangement, where the chain is on top and then the Merkle Tree, because that creates one common master chain. This is two timestamp servers not sharing a chain.
To understand it better, you can try to design a multichain scenario from scratch, instead of trying to combine things in backward-compatible way. If you look at the block header structure, with 80 bytes, which is commonly used, and you compare it with an alternative structure, when you want to support multiple chains from the very beginning, then you can see, how these two models are different, and how far from that NameCoin is.
And also, when it comes to backward compatibility, some people believe, that such Bitcoin's upgrade could be done only by some hard-fork. But I believe, that it can be also done as a soft-fork. For example: currently, the only counted Proof of Work is placed in the block header. However, if you imagine a chain, where transactions are grinded, to begin with many zero bits, and if you create consensus rules, to follow not only the heaviest chain of headers, but also the heaviest chain of accumulated work inside a given merkle tree, then you can notice, that it is possible to require a higher Proof of Work in a soft-fork way. And in general, this is what is needed, to distinguish between two potential chains of accumulated work, and follow the stronger one.
Sometimes I wonder if Satoshi is still with us, in case he is one person (not a group) and alive
He may be alive, but I don't think he is still interacting with us. Leaving the project was crucial for its success. You can see many altcoins, and their creators, which can highly influence the direction, and how "the creator said this" can negatively affect it, by making things more centrally controlled, than they should be.
Also, it is quite important to not come back, as long as it is possible to send any "I am Satoshi" signal. When all ways of proving, that someone is Satoshi, would be cryptographically destroyed (because Satoshi used cryptography from 2009, which may be fully broken in the future, if he will not send any new signals), then maybe he could try to contact with the community, but in general, it is too risky, so it is very unlikely, that he will ever try.
what could he have done after BTC? What are those other things?
There are many things outside Bitcoin, that you can do as a C++ programmer.
At some point I became convinced there was a way to do this without any trust required at all and couldn't resist to keep thinking about it. Much more of the work was designing than coding.
See? It is all about having some simple idea, and constantly following it, until you make it. And it is not that easy to come up with simple ideas, because people tend to
overengineer things:
Because of that, I wanted to design it to support every possible transaction type I could think of. The problem was, each thing required special support code and data fields whether it was used or not, and only covered one special case at a time. It would have been an explosion of special cases.
And I guess, if he is alive and well, then he is just jumping back and forth in some overengineering trap, where you want to design a perfect system, and you are unsatisfied most of the time, because your solution is too complex to release it.
Edit: By the way: Satoshi explicitly said "50 domains per block", while NameCoin simply started from 50 coins, and making a domain means burning 0.01, which means potentially starting from 5k domains per block, and including a system of coins, instead of a system of domains in the first place! With amounts! With fees! With additional coin supply, where none of that is needed, if you would want to integrate it with Bitcoin instead, and use BTC to pay for domains!
