Vulkan is great, BUT!
At this moment AGK2 is in my opinion one of the last easy to use creation programs for OpenGL ES 2.0. That means, I can create apps and games for the OUYA, Raspberry Pi, Low-Spec devices with e.g. Intel Integrated GPUs. Also Settop-Boxes like Amazon FireTV Stick.
Vulkan needs OpenGL ES 3.x compatibility on the hardware side.
So the great thing in Vulkan is better performance, because we can better select between GPU and CPU. But the OS and the chips also need to support that as well.
So no older Android than, I guess, Android 6.0 support.
Great is, that if we use Vulkan, we can use ASTC, a new type of texture-memory compression. So no JPEG or PNG or full Pixel-Images in RAM handling.
At this moment we have only 32 Bits per Pixel for textures. It is a waste of memory. With ASTC integration we could have only ~4 bits per pixel (may vari in quaility) so we could save about 7/8 of the memory in GPU RAM needed.
that could make out of a 4k x 4k texture from 64 MB in RAM only 8 MB. And we could have ASTC files instead of PNG and JPEG, so no decompression needed. That would save a lot of loading time.
The downside is, that it will only work on newer hardware. I guess, the new Amazon Fire TV Stick 4K e.g. supports OpenGL ES 3.1 and so Vulkan. (Geforce 600 and up) But maybe you have a GTX 460 or so, this card supports Microsoft DirectX 11, OpenGL 4.1, but no Vulkan.
Intel GPUs (Intel 6th, Skylake) from 2015.
So yeah, for new projects it is great, and maybe in 3 years all people have upgraded to Vulkan compatible hardware. But for projects in the near future or older projects that target older hardware, I guess, it does not much.
Also AppGameKit is in my opinion for more independent developers. So in this case, the question would be, how to benefit from Vulkan visualy? Higher textures are possible, maybe more complex 3D objects and so on, but is it realistic, to create these complex worlds with AppGameKit?
For that we would also need more multimedia tools like 3D environment placement tools, animation tools and so on. So Vulkan is great, but I hope, that we have a fall back to OpenGL ES 2.0
I tested Unity 3D with OpenGL ES 2.0 and it was terrible. And Godot also only supported OpenGL ES 3.1 in the last release and they are working on a OpenGL ES 2.0 renderer, but it has, from what I read, no good performance at this moment.
So OpenGL ES 2.0 and AGK2 will be my favorite for a while.