The answers for the future - a thankless task, for "to look to the future can not just all..".
But in the present stack is Python (django/flask/tornado, etc.) - the unclaimed in the development of web-backend of the popular/widely used. To see this, it suffices to study open data where it is convenient - hh, moikrug, upwork, etc.
Ie pododvigat to the chunk flask, Jung and so on?
They are there for a long time. If now to hold a sofa dimension, for example, the moikrug service, we get a top number of vacancies:
1. Go - 135;
2. RoR - 121;
3. Node.js - 88;
4. Yii - 70;
5. Symfony - 53;
6. Laravel - 50;
7. Asp.net - 46;
8. Django - 42;
9. Flask - 14;
10. Tornado - 4.
The trends are clear. Despite the fact that each of iron heard "news" and "opinion", they say, have all RoR, node.js/go - stillborn and non-viable crafts, and python is the silver bullet for all cases, almost the best language, but django is perhaps the most thoughtful and competent back-end framework...the market reality shows the opposite picture.
Not with such a rainbow this backend in python, the future looks even more doubtful, especially adjusted for current trends. The catch is that you inflate it out of all the info-gaps hype around python (thanks to ML, big data, etc.) did not contribute to improving the relevance thereof in the web, on the contrary. In the end, and now we have a situation in which competition among python developers exceeds the values in php/js/java, but works for them - tears (compared with colleagues in neighboring stacks). As for the past - the Python 27 years, gange 14, draw your own conclusions.
PS I don't mean that python is a bad language, and django/flask/tornado - bad/retarded frameworks. Just just broadcasts the market situation on the basis of open data:)