Your scenario is likely, but somehow I believe that if they were in nelotihical stage of development, they would be treated even worse. My first guess is that humans would take few specimen for vivisection right away and few others to hold in captivity and research.
Another thing to take into consideration is not only technological but also spiritual development of the planet. I was about to write that we might see somewhat different scenario if we discovered some interesting psychedelic in abudance there, but then I remembered the Dune.
Either way I believe that we would be fundamentally influenced by different approach to life they have over there. That would play the key factor on what our course of action would be.
This is why I wrote this post. To see different opinions, and have fun thinking about it. I have two major issues that I didn't mention here.
Is intelligent life possible in another form than carbon based creatures
When intelligent life evolves does it go through the exact same stages as did the humans went through
Now these queations are material for two more posts :)