This is how they extended my hardwood into the kitchen. This was before sanding. Afterwards, you totally cannot tell that there is a transition. In your case, though, it would only work if you planks line up. Hope this help:

When we pulled out carpet and found this:

We contemplated feathering in boards, but instead did a decorative inlay, with this result:

So yes, I think you could just put a perpendicular board in there to form a visual separation between the rooms.

http://www.pinterest.com/pin/210754457533698010/

If the columns are landing in the middle of that bare spot, it makes sense to highlight it with flooring running between the columns. Use boards as close as possible to the original floor width and have them flush with the old floor. Stain as close as possible to the existing colors and the difference in grain direction will make it blend in.

Feathering in flooring across that spot is possible - IF you have matching flooring and can remove boards in an erratic pattern.