I believe he was referring to liquid cooled cables.
Those also have already been seen in combination with V2 superchargers at at least one location. If the cables were the limiting factor rather than the cars, that combination would already allow higher rates than anybody has reported (the superchargers are not the limiting factor, at least in the single car case).
It's not clear to me whether Tesla's liquid cooled cables also cool the connector - obviously they will do so to some extent, since the cable is one of the main routes for the connector to dissipate heat. Quite possibly they also take the cooling loop inside to more explicitly cool the connector.
So there's a bunch of stuff that we know about already that could make modest upgrades to capability. To date, "V1", "V2" has referred just to the cabinets (the two generations of cabinet have been used with various versions of the stalls/cables), but if they want to make a big announcement about it they could choose to call it "V3". However, last time around the "big announcement" (120kW charging vs 90kW) was made over a software-only change, while the V1->V2 hardware change was just quietly rolled out rather later without fanfare.
I'm not expecting any improvement in max charge rates for existing cars from any upcoming changes (except perhaps a small improvement for '100 cars). There's also limited possibilities for the Model 3, since the two things we know so far point to slower charging in kW terms: it's a smaller car with a smaller pack, so (if built from the same cells) would charge at a lower rate in kW terms even if it's charging at the same rate in MPH or percentage terms. We also know that it has larger form-factor cells, which makes them more difficult to cool (less surface area for cooling), again reducing the potential charge power. It's quite likely that there are chemistry improvements going in the opposite direction, but they'd need to be huge to take the charging power much above what we have today on Model S with large packs. Even existing Model S power levels on the smaller Model 3 battery would be a big improvement in actual usability while needing nothing more than the superchargers we already have.
So if there is a big change to come in the Supercharger hardware, then I'm more expecting improvements to improve the multi-stall sharing and the equipment cost. A single cabinet giving 350kW shared between 4 stalls for example would be a nice improvement in usability, while also cutting costs and reducing the size of the equipment compound (maybe helpful to allow room for battery storage?).