How far does the tree go?
First of all -- thank you SO much to the contributors who built this course! It's been a pleasure so far. Dankon!
I'm currently 8/44 units into the tree. What level of ability should I expect by the end, and what does the tree leave out? E.g., for German, I was maybe at an A2 level at the end of my tree and not able to have many conversations, but I could at least understand basic interactions. Esperanto, of course, seems quite different, and I hope I'll find it easier to put into use...
It's not that easy to say. I'd say A2-B1 in understanding and reading. The Esperanto course has fewer words than other courses (not the fewest, though), but since you learn a lot of affixes, you can combine them to much more words that you can use without never encountering them here, so maybe you will be even better or climb to B2 in a short period of time, but that's just a guess on my end.
Does Esperanto has same levels like other European languages (A1,A2 etc) ? Is that possible to get such diploma for Esperanto?
The tree is considered a little short but there will be a 2.0 version of the tree. If you scroll to the "Trimming the skill tree and releasing our course earlier" update on this page you'll see it said there. You can see the rest of the tree after "Communication" and "Abstract Objects 2" here.
So there is a little more of the tree to learn from but I'd still say A2 or B1.