I think wpf is slowed down for a good reason, it is mature, let’s not forget it’s been there for a long time (including internally in Microsoft long before it was shipped with .net). I’m pretty happy with the state it’s in and more development happening outside (third party controls etc). But having the source to port it would be nice.
It wouldn’t make sense to port it to mantle at all, having a DX12 renderer might make sense (it’s mantle-ish) and will be supported by all graphic makers (unlike mantle). Also don’t expect much out of it except maybe if you’re doing very very heavy 3D rendering in wpf. It wouldn’t change performance at all (you’d be hard pressed to find a case where you’re CPU bound on GPU operations in WPF, or even any case where you’re graphically bound at all vs limited by the speed of your own logic). It’s already very fast and the diference between DX and mantle is irrelevant since there aren’t thouthand of state changes per frame here, the big performance simply comes from the rendering being hardware accelerated vs previous software only solutions and from the well designed Framework and UI virtualisation.
Edit: as for crowdfunding that’s really not needed, if it was open sourced there would be a quick effort to port it i’m sure (i’d be happy to contribute personally as long as it’s open sourced in a way that lets you port it and doesn’t tie your code to the open source world, if it means i can use WPF as a compiled dll on other platforms without any patent / licensing issues i’ll be more than happy to work for it).