I believe EK has downgraded that flight to a 777. Seat Guru, although a great resource is often not accurate with equipment swaps and what not. I'd go with what is on the EK site shows. Did you book using EK miles? If you do a dummy booking what does that flight show? I'd go with that.
I splurged and did a Alaska F miles booking. The booking process at Alaska and Emirates both show the plane as an A380. When I used my record locator at the Emirates site to select a seat, it shows as a 777.
While the route is currently a 777, I assumed that the upgrade was planned for the spring.
My current plan is to wait until couple of months or so before the flight to see what the the plane status is. I've booked a J flight on Delta at 85k that I'll take if the EK stays the 777. If the A380 is flying, I'll take it. I just don't want to burn the extra Alaska miles for a 777.