Okay, so I'm just gonna sit down and try to work on an artist people haven't made many guesses on yet. Any progress is good, and at this point I feel like mods are mostly done giving hints, since the pups are going to start growing up soon! So, I've got two pups that I think might be
Jadeghost's!
The first dog being this little one! One of my personal favorites.

Now, I know that Jadeghost doesn't use a lot of lineart edits, so just wait a bit before jumping on me for that. :P
I'm going to point out that while her past edits have been small there ARE some edits and additions! Her 2015 dog for example.

It had all the cute flowers added, which were obviously lineart additions. I personally think the line style is kind of similar though! Comparing, in particular, this pups hair and tail it looks like a decent match in my opinion. c: As does the eye style, which is a big thing I use to identify artists. Now, as for the hints.
First, I know JG said
"You may be getting warmer. My dogs do tend to have plant themes don't they?" Howver this isn't a 100% confirmation that this years will, of course. Another hint, however is
"My adult dog has a theme." and I think this dog could easily have an intended theme, and it could be plant related for all we know! Afterall, her 2015 dog was decorated with flowers, and yet had no signs of any before growing to adulthood.

Another thing is the line
"keep on climbing though the ground might shake" that was found in Jade's signature in transparent text. A sort of "you can do anything, tackle the forces that go against you" sort of line, and I think this dog matches that very well.
This is also a tiny thing, but Jade's dog is named Lysandra, and I think that would be a nice name for this pup, though I know that doesn't really count as evidence haha~
Now, for the second pup!

Again, for the line edits, this pup has a few but they're minimal. The cucumber and the face are the only ones, so this would match better with Jade's track record of little-to-no line edits, especially for the pup stages. I also bring this pup up because of the cucumber slice. Jade could be trying to throw us off, as we'll likely look for a more OBVIOUS plant aspect to the pup. However, cucumbers are plants, and it's one of the central parts of this puppy. :P For all we know, the plant aspect could be very played up in the final stage, like her 2015 pup.
That's all I got for now! But I hope this helps, or maybe gets some other ideas flowing! c: Just my ideas, haha~