The Deal With Vita
In the absence of any updates to the contrary, many people have said that the Vita version is canned. Not true! Honestly, though, it's kinda hairy how it all unfolded - the original plan was that Mono would come out for Vita and I would just port over the same code I used for PS4, but I think something happened with Xamarin, and the Mono port never materialized (perhaps they wanted more money from Sony than the Vita games could reasonably return? I don't know the details, this is just a guess). But then a small miracle happened and the folks at Sickhead (who also develop Monogame) started developing a C# to C++ cross compiler, and Sony asked them to do the Vita ports for both AV and Towerfall.
The really great thing about a C#/C++ cross-compiler is it makes it possible to port XNA/FNA/Monogame stuff to all kinds of platforms without having to involve Xamarin in the picture. So when PS5 and XBox Two or whatever come out, I won't have to switch over to a whole other engine just to support them. And bypassing the virtual machine should also yield some performance benefits.
The downside is that this work is really, really hard. Originally they were thinking the tech would be ready in June, but it's obviously slipped. C# does a great job of shielding users from complex native underpinnings, and this is what Tom Spilman and folks need to replicate in full. From what I gather they have Towerfall running to some degree but AV is a more difficult beast in terms of things like executable size, memory usage, graphical complexity, etc. My personal prediction would be it'll be ready late this year, but it's hard to know for sure.
But it is coming.