Now that we have parameter packs, the old plan of hard-coding certain tuple conformances directly in the compiler is obsolete. A more recent pitch that reflects the current plan is here: Pitch: User-defined tuple conformances
The blocker at this point is just that the parameter pack implementation is incomplete. Once some holes in SILGen are addressed, it would be pretty easy to finish the remaining parts needed to bring up tuple conformances to Hashable, Comparable, and whatever else (CustomStringConvertible perhaps?) in the standard library.