Well, there just aren't any real strong possibilities left, but
I've kept these here just in case:
m3dplayer
In the savegame and other files in realMyst, there are several references to
what appears to be a 3d player model. At first, we thought the YourInMySightsNow
egg might trigger the 3d player. That hasn't proven to be true (so
far), so I've now put this in the category of a possible egg. Let's hope
Spyder doesn't take the rest of the year off.
Ides/Break-in
The "Ides of March" and "a
break-in at a famous hotel" clues from 9 March would seem to be connected
to the "Kong" egg, at least according to the theory that the clues
line up across the different dates. Yet no one has conclusively shown why
they are needed, as that egg can be solved with only the other two date clues
from the following week, "Sam Clemens and Sir Winston" and "Radio
4 announces a new hyperspace bypass." This has produced speculation
that there is another egg hidden inside the planetarium monitor, although
countless attempts to find it have proven fruitless. For that reason, I've
also listed this as a possible dead end.