I have done very little coding, but in my opinion, this is why I think Eden 2.0 hasn't came out yet.
Half Sized and Double Sized blocks: Ari did state that the half sized blocks might not come out in the 2.0 update. I think its becuase of the amount of blocks and colors. In the game, there are 54 different colors that you can change your blocks into and there are 28 different blocks. If each block gets 54 textures (which they do) there is a total of 1,512 different textures. And if there are 28 half sized blocks and 28 double sized blocks with all of the colors, that would mean that Ari would have to design 3,024 different textures not including the new 2.0 blocks!
Half Sized Blocks: There could be another reason why Ari might not be adding the half sized blocks. And that is becasue in Eden you can place blocks pretty far away, and a half sized black is 1/4 the size of a normal block. if you placed a half sized block, where exactly would it be placed? in the top right? in the top left? In the bottom left? in the bottom right? Placing those would be a pain and that could be a reason why those might now be coming out yet.
The Terrain: I know very little about this, I could be totaly wrong. I have played riverbeta before and noticed that it took up a whole GB of space. It kind of makes you wonder how much space the final product will take up (and the fact that there isn't any bedrock). I have coded in 2D terrains before, but not 3D terrains. I'm not really sure how hard it is for 3D, but Ari did state that he would be tweaking the terrain until release. Mabe he could be trying to save space so it doesn't take up that much.
Motivation: Yes, I had to put this on here. When it comes to posting on Eden, there are always a bunch of people that are not patient that are sore losers that need to get a life. Ari even commented that we are mean to him. I have said this before on the FaceBook page, but what if everyone was nice to him. Instead of saying stupid things like, "when is the update going to be out" what if everyone greeted him when he would post again (that might be the reason why he isn't). Don't you think that if everyone was nice that the update would be out already. Ari would have something to look forward to when he could come online and see all of the postive comments on his page saying things such as, "Take your time, I'm patient" or "its nice to see you again!"
Something Special: In every Eden update there is always something that we get extra that Ari never said would come out. For example, In 1.7 it was all about creatures, but when it came out we also got better sound and music. Mabe for 2.0 the adventure mode could be coming out, or something else big!
Hobby: For Ari, Eden is just a hobby because he has to work a full time job. Of course all of these reasons could be reasons not to be looking forward to finishing this update. It's a lot of work for one person.
In my opinion, Ari has lost his motivation for the update again. It's fine with me. I'll play Eden forever. I hope this was easy to understand, this took me about 30 minutes to do because my internet crashed when I was about finished and lost everything. I hope you guys enjoyed this and tell me what you think :)