Way to early yet I don't see it becoming to valuable for at least another 5 years or so, unless you have a one keyword domain in that extension you could do well now..
Unless it is a really great keyword, I don't think you will ever get more than a high $xxx, and only if you found an end user. The .bz extension is just not that hot, and in my opinion, I don't think it ever will be.
I sold www.News.bz (4L) for $200 about a year ago. Good luck.