I read somewhere in the forums which mentioned that if you released a pokemon with a high happiness factor, they would return. I have a few questions concerning this.

1. Is this at all true?
2. If 1 is "yes", then how does this process work?
3. How long does it take for said process to work.

I'm not yet willing to dedicate one of my high happiness pokemon, so I would appreciate any input on this subject.

I have not tried, but yes, I believe this is true. I think it happens as such: you select a pokemon in your box and choose to release it, and it immediately comes back, with a message saying something about the pokemon missing you or something similar.

Not true. This is the (possibly) only reason why the released Pokémon came back: that Pokémon is the only Pokémon you have that knows Surf.

Why would the fact that it knows surf have anything to do with the release and coming back factor?

1.) Yes
2.) If the happiness is high enough, they actually won't even leave
3.) Happiness > 180 or something

Happiness guide: http://www.psypokes.com/lab/happiness.php

If the pokemon is the only pokemon you have knowing a certain HM, then it won't be released. This works with all HMs, not only Surf.

Maybe Nintendo designed the games so that you won't be trapped on an island forever?

Yes, that is why; Just like Fly. They had to make sure that, at all times, you have a means of transport out of wherever you are at the moment. Otherwise, you may be trapped somewhere and unable to make it back.