I believe you mean you want the user's account to automatically be created when they click the Login With LinkedIn button. If so, that feature is coming. LinkedIn's developer tools did not allow us to fetch the user's email address until very recently (August, in fact). Once they enabled that, we immediately released the latest version which allows the user's email address to be imported for an easier registration process. Without the email, previously, we always had to show the registration form so the user could enter it (since you can't create a Joomla account without one).
The next release, due out in a few months, will have the automatic registration/account creation process I think you're looking for. That's been a part of our Facebook extension for years, and is definitely one of the most popular features. We've been very excited that LinkedIn now allows access to the email address (it was a bit of surprise when they added it), but not it will take a little more time for us to implement all the features that that allows.
Existing users on your site can easily associate their existing account with their LinkedIn account to allow for single sign-on access in the future. That ability exists in the current release of JLinked.
Hope that explains. As always, we have a 30-day money back guarantee. If you aren't happy, feel free to request a refund.