NotifyCorp, the makers of the wireless email and PIM bridging middleware software, NotifyLink, has posted a new teaser for the Pre on their website. The previous teaser only stated that the new client was "coming soon."
As you can see, the teaser says that the webOS client for the Pre will be arriving in September. There is no word at this time whether or not you will need to upgrade to NotifyLink Enterprise Server 4.7 or if you will be able to plug the new client software into existing NotifyLink 4.5 or 4.6 servers.
I'll post more details when I get them. If you are not familiar with NotifyLink, you can learn more about it on the NotifyCorp website.