I agree PDX to LGW is not on the cards. Not ven sure LHR is either ! There is already a long list of destinations VS want to serve and no one of any importance thinks PDX is on it.
If VS thought a US flight (other than the bucket and spades to MCO and Vegas) from LGW was going to work it would have happened by now.
If there is growing demand from PDX to AMS then let KL/DL pick it up - after all most people want direct flights.