When is the SNAP API for Python 3.5 is coming?

I’m sorry to hear that you are already waiting for so long.
Unfortunately, over the last year the development more or less stood still, but now it is starting again.
We are currently planning which issues will be done and when will they be done.
I can say that Python improvements have a high priority but I don’t dare to give you a specifc date. If I say, in half a year and it will not be available then, you will be disappointed again.
There are many issue and features with a high piority on our list. Unfortunately, not all can be done at once.

In the meantime you could have a look at these threads. Some got it to work.