Welcome to WebmasterWorld Guest from 18.104.22.168
One time someone asked me what my site was about and after my explanation - they replied "oh don't bother I don't understand what you mean", so better not make this site too complicated.
If it's a sales site, then keep it as that. If it's a portal, keep it like that. Don't mix and match different ideas, or you'll confuse people as to your site's purpose.
If you want a forum, then fine. But keep the blog and forum seperate from the sales/product site, and you won't risk confusion.