The fact that the stand can accommodate up to a 777 doesn't necessarily mean a 777 service is going to be launched. Let's remember that UA, AC, QR, EY, TK and many other airlines which serve EDI all have the 777 in their fleet. This development means that they can fly in a larger aircraft and still have direct terminal service rather than shoving it over to a remote stand or having to rely on steps. It could be a bit of much needed forward planning for EDI.
If a new airline is coming to EDI then it is unlikely to be EK, the only other viable 777 users who may launch a route would be CX or CA in my opinion anyway.