A job posting by Motorola directly attacks the X-Phone rumor. The posting is looking for a Senior Director of Product Management to work on the X-Phone project. The LinkedIn job posting has since been pulled, but people managed to screen grab it before that could happen. Take a look for yourself.
There's a few issues with this job posting. First, if they are hiring someone to work on the X-Phone now, it would indicate that development is still early. This means that rumors of a device being ready to launch as early as Google's I/O conference are likely incorrect. Of course, going off of a job posting is quite difficult to do, so this could be wrong.