I registered this domain a while ago.. 'wineightforum.com'. Any copyright issues with microsoft and also possibly I will put a windows 8 forum on it in the future.
It will likely be less of a copyright issue than a trademarking issue. Read up on trademarks and trademark infringement cases and you might get a better idea. It will probably come down to whether MS think you're infringing any 'Windows 8' or similar trademark, device or brand that they use now or in the future. The fact that you've called it 'wineight...' rather than 'Windows 8', may work in your favour but you're best to do your homework and get expert advice before you commit funds.
That is a trademark issue. Although Microsoft in the past has been aggressive about protecting its trademarks, what you are proposing (and of course no one has actually seen the site), there is absolutely no clear answer. My initial thought is you'd be fine. The bigger question is whether you'd be willing to fight, and afford it, if there was a dispute. Doesn't seem like that is the case as the domain is up for sale instead of putting a forum on it now with threads such as: what you you like to see in a version 8?
It is not the domain name that is going to be the issue, it is the use of the site. If your wineightforum.com is used for a non-software site, or as you suggested, as a public forum on windows 8 you would have an arguement that you are entitled to the domain. However, if you try to make money on your site by selling a product that competes with MS you will then have a big problem.