FYI -- Ordered a King Ranch with Soft Tonneau cover option. Here is a Company update I received just today:

"Your 2015 F-150 order includes the ‘Remote Start System with Remote Tailgate Release’ which is standard content on the Platinum and King Ranch Series, and on the Lariat Series with the Mid and Luxury Equipment Groups (501A and 502A). The Hard and Soft Tonneau Covers (listed below) will not be available with the remote tailgate release until 4th quarter 2015.


•Tonneau Pickup Box Cover – Hard (96X)
•Tonneau Pickup Box Cover – Soft Folding (96T)"

 

I ordered a 2015 Platinum with the Ford soft tonneau as well. Found out the same as you did. Dealer removed the option and the truck went on into production on April 2nd.
The dealer will install a different brand that's supposed to work with the remote tailgate.

 

Here is another note on it:

Soft/Hard tonneau covers - 96/T96X with Remote Tailgate are not available until 07/06/15

http://www.donlen.com/production-trucks-ford.aspx