This will never happen and I'm 100% sure of it. Allow me to explain, I've been a freelance translator for 18 years.
Machine Translation cannot differentiate between how words are being used in different contexts. Take for example the word "handle" in English. We use this word in English in about seven or eight different contexts, namely:
to defend (handle oneself)
for a name (what's your handle)
These are just a few example. Now let's look at the nouns:
handle on a basket
handle on a drawer
handle on stretcher or wheelbarrow
In Spanish, there is a different and specific word for each one of these "handles". It is impossible for Machine Translation to ever know this. Sometimes the wrong word is used by Machine Translation. For example, it might utilize the word handle (door handle) for handle (manage).
I'm only talking about one word, here.
The only time that it might be advantageous to use MT is if you're a translator who can later edit Machine Translated text. I can tell you that for most translators, this is a waste of time. Most translators prefer to translate everything than to rely on MT only to later edit everything that was automatically translated.
If you want to convince yourself of it, try this. Go online to any news site of a Spanish-speaking country, like say, Argentina. Take some text and paste it into a MT program or engine to the language you understand. See the results for yourself and come to your conclusion.
Finally, unless you can "handle" editing text from automated translations, I wouldn't try it. Always rely on human translation.