Well one thing that I have always done and always will do is never to rule anything out unless I have irrefutable proof to do so. So am I not ruling out any prospects of EK coming to LTN but I personally do find it very hard to believe they would choose LTN over STN.
If operating from LTN restricts them to an A330 or even potentially put a limit on how long they can viably operate the route for, I don't see any commercial logic in even starting it regardless of any offers made.
This is not me having a dig at LTN or acting as a STN fan boy/supporter of any form but what STN can and will provide for EK flights if they were to operate from there in future in terms of facilities and infrastructure wipes the floor with what LTN could offer, certainly on any shorter term prospects.
I guess we will just have to wait and see what happens (if anything) in the future.