[microcolonel]

The largest two components in 3D acceleration are the userspace shader compiler/GL library, and the display configuration code. The latter is in (usually) the kernel these days. They should have no particular issue forward porting the kernel side of the equation, but if they want full open source 3D acceleration, they are going to need to write the userspace part of the driver (or more likely, port Mesa to it).

As for WiFi, not sure. The drivers could be crappy in ways which don't cause problems on Android; or (rarely) could rely on a userspace component. Otherwise they just haven't gotten around to it.

Also, both of these problems would be specific to a given device (or at least a given chipset). Which device are you talking about that they are having these problems with?

As for Replicant specifically, they are only satisfied with free software, right? I don't think they would even want to forward port the graphics drivers, since unless there's already enough development on an open source driver to warrant upstreaming, there's probably not a workable open source userspace to match the driver anyway, so they wouldn't distribute it either way.