Is there a macro to turn Raze into Ravage whenever Ravage is available?
There is not. Blizzard doesn’t want macros to be a replacement for players deciding on an optimal ability based on the current situation.
Set a weakaura to notify you of Ravage becoming available, and make a mod-macro to put them on the same binding slot… Like this…
#showtooltip
/cast [mod:alt] Ravage; Raze
Do a cast sequence: raze, raze, maul. With a short reset. Maul will turn into ravage when available. You can tap it to raze, or spam it to use a procc’d ravage. If no ravage is procc’d you just thread a maul into your raze stream.