But uptick is not significant enough to say that they have enough momentum.
Most companies like amazon write services in lots of different languages. Just using a language is not enough proof, do you have examples of major services written in functional languages at these enterprise companies?
Agreed there need to be "more" wins, but the amazon service seems like a pretty big one.
From: https://lispjobs.wordpress.com/2014/11/25/clojure-software-d...
CORTEX is our next generation platform that handles real-time financial data flows and notifications. Our stateless event-driven compute engine for dynamic data transforms is built entirely in Clojure and is crucial to our ability to provide a highly agile response to financial events. We leverage AWS to operate on a massive scale and meet high-availability, low-latency SLAs.
I don't know if the trend will continue (my guess is yes), but you shouldn't dismiss it just because C, C++, and Java are still the most widely-used programming languages in the world.