Remember that floobits are the people that threw a tantrum when upstream vim wouldn't accept their patches, and have a vested ego interest in pushing a vim fork.
Eh... unless there's more to the story that I'm missing out on, I don't think it's fair to say they "threw a tantrum".
Basically, that company has a service that lets developers do real-time collaboration. Like working on a Google Docs document... except that it's for code, and collaborators can all use whatever supported editors they like. When they went to add support for Vim, they ran into problems with the "real-time collaboration" part... because Vim is single-threaded and doesn't have a non-blocking event loop:
The Vim maintainers kept rejecting it, for different reasons each time. After two months of back-and-forth, the Floobits guys asked the Vim guys to either give a comprehensive list of things in the patch that need to be different... or else acknowledge that they simply don't want the event loop thingy merged at all, and that Floobits should move forward with their own fork of Vim instead:
Personally, I don't have an opinion one way or the other on the merits of that patch. However, I think the Floobits guys were justified in feeling frustrated about the Vim guys dragging their feet and not being completely forthcoming.
Either way, if you do some quick web searching, you'll notice that Floobits became pretty big fans and online promoters of NeoVim from that time forward! So much so that you kinda have to take it with a grain of salt.
I'm not exactly sure what to even think about NeoVim. They've been plugging away for over a year, their GitHub repo has over a hundred contributors and two-thousand commits, and yet it's still pre-alpha? Also, the primary purpose seems to be allowing people to write Vim plugins in any programming language. However, it's not like the Vim ecosystem is hurting for plugins today. Besides, the whole point of "vimscript" is that it's self-contained and baked-in as part of the editor. Totally cross-platform, and always there. If I install a NeoVim plugin, then I have to make sure I have the right version of Ruby or Python or whatever on my box to support it? Yuck, no thanks.
As near as I can tell, any real value-prop for NeoVim is using it as an embeddable component. Like the Cloud9 guys' cloud-based Ace editor (http://ace.c9.io), or as something that IDE makers could bake into their desktop IDE apps. I don't really see what's compelling about it head-to-head with standard Vim, assuming it ever fully ships.
You're the one whose bad patches were rejected, you just dug through a year's worth of my comment history, and you're constantly and heavily promoting a terrible-design-and-still-no-beta-even-after-a-year-and-a-lot-of-donated-money fork of someone else's open source project ...
Neovim will have Lua (and LuaJIT) baked-in too, so Lua will always be there.
In my opinion initially there might be many different languages used by developers as they try out the new versatile plugin infrastructure. But after a while only a few languages should emerge as the dominant ones, because developers have the desire to help as many people as they can by making their plugins easy to be deployed and configured. I would guess Vimscript and Lua(both baked in), Python(nowadays it's practically ubiquitous) are the more popular choices. Personally I like Go (fast, easy concurrency, and single executable deployment).
