Can I Import More Than Once?

I’m in the process of creating a new WordPress site which will combine elements of my current html site and WordPress blog. I imported from the current blog to the new site to see how it would look, and everything is just fine but I have a question.

I won’t be ready to launch the new site for a few weeks and in the meantime I will continue posting to the current blog. If I import again when I’m ready to launch the new site, will the posts be duplicated?