Age is not the primary factor, but rather the economics. And since EK leases its planes from all kinds of lessors with individual contracts per airplane, I assume A6-EBL could have been one with a less favourable contract to be continued / renewed. (Just a wild guess)
Apparently, A6-EBL will go to Rossiya.

Here is a fun fact: On 22th Aug 2012, a baby was born en route to MNL aboard A6-EBL. The mother named the baby "Ek"

Another info: All A330 and all 340 have now left the fleet as of 30th Oct. This makes A6-EMK (772ER) the smallest aircraft in the EK fleet. (will leave soon too, though, making the 77Ls the next smaller ones. )