Yeah. I'm just as surprised about the Lisp resurgence as most.

Short answer. Yes, Clojure is more than capable.

Long answer. Ruby didn't really bring much to the table, and in fact it took a whole lot away (the JVM). It's still an imperative language.
Concurrent programming is coming fast. Hell even my phone has four CPU cores and yet we're still happily writing single-threaded Java code. Functional Programming solves a lot of the problems we're going to face in the now pervasive multi-core environment.

Scala. Scala is an amazing language. My concerns with it are it's complexity and the fact it's a hybrid. It is very easy to slip back into imperative programming in Scala.

But I can foresee an army of Java developers swarming to Scala and immediately writing imperative-style code (in the same way we had armies of C developers writing procedural-style code in Java) when they make the switch.  Thoughts +Bryan Murphy?

In Clojure, you simply can't as it's a purely functional language. 

Clojure forces you to think about things differently. 

http://clojure.org/state

Good point Deano! Concurrent programming is the key!

I do think the Scala can be useful in bridging the gap +Dean Budd.  Even it your team is dedicated to taking the time to learn/use FP there will be times when their skill set is not developed enough to solve the problem at hand and imperative programming maybe useful.

As and aside I've been looking at some performance stats and functional isn't always the most efficient at runtime (granted it depends heavily on the runtime engine).  An example was in JavaScript that changing a forEach() to a for loop gained 25% performance due to the fact that the capturing of state for closure mechanics wasn't needed.  Therefore being able to use imperative code may be beneficial as well.

The key as always is team discipline which is always the hardest language to learn. hahahaha

+Terrence Miao I completely agree with +Dean Budd re the state of Ruby.  I never saw anything useful in Ruby and now that Puppet Labs is moving from Ruby I see no reason to learn it (other than maybe the odd Vagrant plugin).  I'm selfishly hoping that the rest of the DevOps community sees the writing on the wall and moves away from Ruby to a JVM language, so I only have to maintain one runtime env (JVM + Gradle = able to run any JVM project :) )

Finally +Dean Budd, re your point about mobile, devs can only do as much as their runtime env allows.  Eg: Groovy being dynamically typed doesn't port well to Dalvik/Android.  I see a big future for Scala on Android as you can do FP/OO with the imperative code that is needed for manipulating UIs :)  If Scala's Actors translate to Dalvik then in the future I wont need to write my own multi threaded management code :)

+Kieran Simpson, you don't need imperative code in the UI. Just look at ClojureScript ;-)

Functional programming in whatever language you get/have to use is the future!
Or even the present ;)

I reckon JVM will dominate future programming language development.

I find it amazing when people think it won't :)