Palladium may temporarily become more expensive than platinum but that can not last for long.
Platinum is rarer than palladium and when both are interchangeable for converters then the rarer one has to go back to the price that represents that difference. After all these metals are not the same and one has some uses that the other can not fullfill.
Actually I expect in the near term for platinum to be more expensive than gold. Traditionally it is more expensive.
Where I expect gold to be more expensive then either of platinum or palladium is when the precious metal prices stop being manipulated. I say both gold and silver are at artificially low prices due to them being competitors to paper ( bogous) money.

Just saying to all, short term ok but in long term be carefull of staying too long with palladium.
Ed.