AFAIK the 68k will be completely out of a job, but I guess drivers will (need to?) be written for audio, diskdrive access, HD interfacing etc. Would be a bit useless for me otherwise, having no SCSI on my lowbudget BlizzardPPC :-).
But how do you mean using custom chips 'on the fly'. Do you mean running hardware banging 68k programs? That will be out of the question with OS4 (someone correct me if I'm wrong). OS 3.x-'friendly' 68k progs should have not much problems though, with the built in 68k emulator.
