Sorry, bro, but yeah, I don't see that one coming back. For what it's worth, it actually has been copied. It was used in the very next game (Castlevania Bloodlines). Except in that game, the weapon was a spear, but functionally, it operated like the SCIV whip. I'm sure you know why the SCIV whip was basically shelved, though. It was game-breakingly effective. A big component of the Castlevania games is the reliance on sub-weapons and/or magic and the SCIV whip was so effective that it made the sub-weapons mostly useless. Also, the platforming segments that relied on the whip were.... gimmicky. Whip traversal has been tried a few times. It's never been implemented all that well.
I'm guessing you played SCIV at a pivotal time, cause otherwise it's strange to see it as the most true Castlevania since it's core gameplay deviates so significantly from the rest of the series.