why do you think you need 2 databases to do that? you can run 1000 seperate installs of WordPress using one MySQL database.
thats not what makes what you are asking difficult to do.
What makes what what you are asking hard to do is this:
Consider google.com -- you may go there every day. I do, at least. The content there cant, the actual non-dynamic non-search result content, doiesnt just change on the fly. In other words, unless I give google.com a reason to display the page in German, I may get it in French. There is an impetus, in other words.
In a nutshell, the answer to what you are asking is no. But its not a MySQL limitation, its a "things just dont work that way" limitation.
perhaps you can explain what, specifically, you are trying to accomplish?
Or maybe wp-mu is more what you are looking for,