The GEGL core update by itself brings no new features (user functionality).
I don't dispute that point, but I do not think you realize just how much GEGL support being in will enormously accelerate the features that are currently on hold and waiting on it.
The reason things haven't really progressed very far, if at all, on many of the features that are waiting on the GEGL port to be finished is not because they are taking their time with them, it is because any work that might be started before the GEGL port was complete would likely to be entirely a waste of time, and because trying to implement it without GEGL being in would take a lot longer anyways, GEGL support would probably be in before it was complete, so there's no point starting on something that would have to be entirely thrown away before it's done, and can be relatively easily done once the underlying architcture has been modified to be amenable to it.
Consider when building a home, the most amount of time is spent making sure the foundation is properly in place. Once it is, a house can be built on a good foundation comparatively very quickly. Likewise, once the GEGL port is finally in and 2.;10 is out, you will doubtless be witness to vastly accelerated GIMP development of some of the most urgently desired features. Internally, for all intents and purposes, 2.10 will be almost an entirely new program.