what do you want to do with GEDCOM?
export (download from Familysearch to your local PC)?
upload from your local PC up to FamilySEarch?
Thanks for your questions, I'd like to export it to Ancestry.com
The short answer is - there is no straightforward GEDCOM creation within FamilySearch
However dont take that as your final answer.
There are other means to transfer data between the two systems.
One option is to use a third party system like Rootsmagic
Using Rootsmagic (and other programs like it)
you can download data from FS into Roots magic - Rootsmagic then in turn allows you to create GEDCOMS the way any similar genealogy program does.
Then you can upload the GEDCOM to Ancestry.
Now I am not a user of Ancestry - so I dont know the details of the gedcom upload.
Im sure it would work great the first time - - the question is what happens as things continue to evolve in FamilySearch
and then you want to bring Ancestry in sync with FS. thats where it can I imagine get complicated.
Now I believe - besides the Roots magic method discussed above - I believe there may be a true "synchronization" application/service/program that you could use (I am pretty sure it does not rely on traditional "GEDCOM")
But I have no experience with this "sync" process - so I leave that to any other users who may know more about that than I do for them to explain.
BUT by any means - if you are making updates in both system - trying to sync it all together - I imagine can be less then straightforward and very trick at times - and may or may not force you to do a manual review of each record as part of this "sync") and thus not be as easy as you would hope. I imagine it would be much easier if ALL your changes were on one side or the other - but keep in mind in FamilySearch - it is one database for all million users (its not like Ancestry where each user has their "own database" - that paradigm doesn't exist in FS (its one massive database being updated by all)
any records updated by you in FS - can also be worked on by anyone else.