I'm planning to emulate everything about the GB/GBC/GBA systems as I can. That includes GBA <-> GCN connections, but at this phase I'm just trying to get games to boot. I've set a deadline for myself (Oct. 15th) to get something to boot, and I think I'm making decent progress in that direction. I'd love to implement a "standard" protocol, and if it works, I don't see any reason to start re-inventing wheels. Anything at this point is better than VBA-M :p
Though about Gekko, I doubt it'll ever be finished, or get into a playable state. While Wind Waker and Animal Crossing are playable (Sonic Adventure 2 too, to some extent...) I don't think Gekko is even close to being able to support JOYBUS communications. You never know though... Maybe some super-programmer will revive interest. We have Dolphin, but some people just like to build emulators for kicks, so it could happen.
Though about Gekko, I doubt it'll ever be finished, or get into a playable state. While Wind Waker and Animal Crossing are playable (Sonic Adventure 2 too, to some extent...) I don't think Gekko is even close to being able to support JOYBUS communications. You never know though... Maybe some super-programmer will revive interest. We have Dolphin, but some people just like to build emulators for kicks, so it could happen.