Forgive me if it was mentioned before, but heavyweight torpedoes have a lot of potential left that hasn't been published as capability of in-service HWTs for all I know.
- use of recoverable HWT as minehunting drone
- use of recoverable HWT as contact-confirming drone
- HWT jumping out of water to add more sensor information (radar/thermal) for target selection (or deploying a mast to do the same)
- use of HWT with battery-electric drive as self-deploying naval mine
- use as self-deployable mine but still under control of the sub; basically laying in wait at a strait for hours or days, then going for the target without compromising submarine location
- anti-torpedo torpedo capability (not optional, but sensible if there's an opportunity)
- recoverable HWT that destroys small targets (such as UUV) without sacrificing itself
- battery-electric HWT going silent at slow speed for 20...60 minutes before getting serious about attacking a ship, less likely to compromise submarine location
- triangulation of target locations from multiple torpedoes still with fibreoptic link
- employment of HWT as believable submarine decoy
It's very easy to hide lots of capabilities of HWTs from the public, so I suppose the technical progress in the area is likely decades ahead of what the public learns, and this it not about speed or warhead lethality.