This board won't exist in 50 years. There is a chance, but I for one consider that as as theoretical chance only.
For one thing, people nowadays seem to take the world of today for granted. However, it's only been like this for the last hundred years or so, and even in those years we've had two world wars. 50 years? That's plenty of time for a even a post-apocalyptic world to rise. I don't think we should take it so extremely for granted that things will stay on the same track. Perhaps people discover that there's isn't really any point behind technology. Perhaps the machines take over (this is with an ironic smile, I don't think there's anything to be afraid of).
Even if things doesn't get as drastical, I don't think we will stay on the same track. I do believe that today's capitalistic society isn't here to stay, but that's probably because a part of me is against it...all the buying pressure, all the giants squeezing every last drop out of the commercial-brainwashed consumer. And also, 20% of the humans living on the work of the other 80%. And coorperation leaders earning more than the working people, even if the working people work harder. You might have stamped me as a communist by now, but don't fear, I tend to be reasonable and I absolutely see the advantages of a free market. I haven't really taken a firm stance, I just see that things are wrong as they are today. I'm also very for free speech BTW, there's no way I'm ever going to support forced communism.
The bottom line is, I think the world will change. Even if nothing of what I have described above is true, people won't log on to a board in the future...just look on how the user interfaces have improved in the last ten years. With this speed, we'll have way better ways of communicating than some hacked UBB Perl/HTML board in 50 years.
And with that as a basis, predicting the results of this board in 50 years is difficult to say the least. It can of course exist for a while, being updated to other formats as they arrive. But, things like Usenet is much more likely to survive in some way. I'm more optimistic for alt.games.final-fantasy.rpg as such than this board.