I've been a member of BYOND on and off since about 2003, so I've witnessed the rise and fall of so many potential games before they even got started.

I'd just like to ask those of you who have been capable of publishing a game in a playable state, when did you start to publicize? When did you feel it was the right time to make a HUB and introduce your game to the BYOND community? And when did you take it that step further and try to establish your game outside of BYOND?

I've been working on a game on and off for a few months now, the game's almost in a state that I feel is presentable and offers an introduction into a world of Lore that I hope to expand upon in time.
No better time than the present! :)
I made my hub when I initially started my project and came up with the details such as name and design. Although, still in development (mostly from real life taking development time away), it should soon be released for public consumption. I started the project in 2009 but I am the only one working on it and only when I *feel* like it or force myself.
It is a subjective experience, it depends on you and your project. Whether you want to develop a complex game with a lot of content or if you just want to make a simple chess game really can make or break your byond experience.

Most people come into byond wanting to make a giant MMORPG and that is like going to Mount Everest for your very first hike. You probably won't be successful!

It really is up to you to decide if you are ready for public exposure, if you think you have enough details or merely don't care and want to get it out of the way (creating a hub). It also exposes your project to the outside world which will generate interest in it before it is even released. This is one of the reasons I am releasing "how to play pondera" posts before the game is even released, people will know how to play before they even start the game!

It really is up to you, it is your project and you control all facets about it. If you think it is ready for public consumption or exposure, what are you waiting for? Make a hub and join in on the fun! :)

As for establishing the game outside of byond, you'd really need a gameplan for that (and a functioning project). NEStalgia is about the only project that has successfully done this and no one really knows SilkWizard's secret, other than that he is a wizard.

You'll just have to submit your project to steam greenlight or some other outside source of influence and see what happens. Personally, I am not thinking that far ahead anymore (initially I was, but not now). You want to release your project and generate sufficient interest in it before you commercialize it (your results will be that much better if you do).
Depends on the game, is it playable? If its not, don't show it off.

Is it finish-able? What type of game it is will depend on whether the answer yes or no matters or not. If its a role playing game, does what content the player can access be enough to wet their tongue and keep playing/come back later to play when its more complete. If it is more casual, puzzle, board game etc can people play competitively against each other with the current rule sets provided.

If your mind is telling you that is "almost in a state that I feel is presentable" then make a list of what things it does need to get it to that level, and try working on only those points until they are done.