The latter isn't relevant - Facebook has full access to the data and likely has some major index to tie the two together. The simple communication data from Whatsapp alone is enough to find enough reference points for a high-confidence match with a Facebook profile.

As for the former, also likely irrelevant - Facebook has been keeping Shadow Profiles [1-4] for some time now, and whether or not you have an account, Facebook probably knows a lot about you just from what you/other people/your browser leaks about you. This information likely will just be amalgamated into the existing profile.

[1] http://www.digitaltrends.com/social-media/what-exactly-is-a-...

[2] http://www.digitaltrends.com/social-media/what-exactly-is-a-...

[3] http://www.wired.com/2014/10/privacy-friendster/

[4] https://spideroak.com/articles/facebook-shadow-profiles-a-pr...

They store the data until you do (or until you register with a future FB product), if you finally get one they'll link the two together and already have an extensive profile of your behaviour they can now match with an FB profile.

Having the FB account is just the last piece of the puzzle, they already know who you are if you use Insta and WhatsApp

You'll have a shadow account on FB. They do this for all non-users.

In my case, whatsapp asks to connect to my (non existent) facebook account every few weeks!