I've got a friend considering purchasing a new 2014 Prius v (lowercase v) from the dealer. Should they be concerned about potential traction battery issues on a car that's been sitting on the lot for a long time?
no. the battery is stable for quite some time, if the car starts, your good to go. and even if the hv battery needs charging, no permanent damage is done. they may want to request a new 12 volt battery however.
I'd test the 12v battery before purchase. If it is low it would either be a negotiating point or a new battery. Ask about the warranty on the battery. If it is 100% replacement within 3 years it may not be an issue. I tested the battery in my 2010 before signing the papers and that car only sat around for a month or so.