The language is remarked in Scripting section of whycardano.com and at https://www.cardanohub.org/en/cardano-vision-paper/:
we have chosen to design a new language called Simon_6
footnote:
6: Specifics will be released in an upcoming specification. The full language will be supported in the Shelley CSL release planned for Q4 of 2017.
Unfortunately I couldn’t find any information regarding Simon language at https://cardanoroadmap.com/
Have I missed something?
I think Simon has been deprecated and I’ve never heard Charles talk about it. Regardless, Cardano’s smart contract scripting language is Plutus.
Any programing language could be used to write smart contracts for Cardano. Plutus is the prgrm lang invented by IOHK. Please check this All blog posts | Runtime Verification Inc
Yes, plutus is great. But its just another language 
The real breakthrough would be the IELE virtual machine (I’ve posted the link above) As you can see here -https://github.com/runtimeverification/iele-semantics/blob/master/iele-examples/erc20.iele its rather advanced already
Correct, we have to make the distinction here between Plutus, which is the language of the protocol of the smart contracts platform on the CL, and the actual smart contracts themselves that can be written in any K defined languages. And that’s where the IELE VM comes in in order to ensure ultimate compatibility and translate the Smart Contracts so that they can be “readable” by Plutus. It is a thing of beauty 
Here are a couple other posts from CosmosX and I in the past:
@p-alik When Charles says “Yella” in his interviews, he’s referring to the EILE virtual machine.
I believe Plutus is still in development. But I would assume that it will be available when CL is released.
The Contract Layer. There’s Cardano SL (Settlement Layer - for transfer of assets), and Cardano CL (Contract Layer - smart contracts). SL is running now but not fully implemented i.e. still working on getting stake pools running etc. I believe CL will be up and running towards the end of the year. If you go to the website there’s a nice little roadmap with expected development milestones and timelines.
You can build and run Plutus REPL, but it’s only prototype for now:
I stand corrected! sort of. 
Good to see they are planning in their roadmap on building a lot of the tools that make development in haskell pleasant for Plutus. A hoogle-like search hopefully with an emacs extension one day would be great.