Alternate Database Support (question for the devs)

I know this exists in the codex http://codex.wordpress.org/Using_Alternative_Databases

However, the most recent discussion on this topic was 3 years ago. Have any efforts been made for modular (pluggable) database support in wordpress?

My other question is, how many areas within the wordpress code are mysql queries hardcoded? Is it extremely scattered throughout the source or somewhat centralized? If centralized at all, how many files are we talking?

If someone was to pickup the project (which I personally think is essential given that the future of mysql is currently uncertain) where would one start?