If you were going to spend $4k on a cartridge and then $4k on another arm down the road - you would be better off buying a new turntable/arm package. None of the VPI arms are that great, and a change requires new armboard etc.
My recommendation would be to buy the dual pivot option and new cartridge.
Down the road reevaluate arm upgrade vs new TT/arm.
Something like Feickert/Kuzma 4Point9 combo down the line would far exceed the VPI combos at a reasonable price.
I would argue that an upgrade to Fieckert/Kuzma with a $1k cartridge ( example Audio Technica ART9 ) would give you a better overall result than buy-in a $4k cartridge now.