AT,
I believe you are correct in that 'new' fuel does indeed contain a large amout of entrained gas that 'boils' off as outside air pressure reduces during climb. If you loose your booster pumps (due to electrics loss for instance) then the risk of cavitation is high for the first 30 minutes or so when the a/c is above FL170. I think this is the height above which the phenomenon starts to occur.
It is my understanding that once the gas has boiled off then this chance of cavitation ceases to be a problem. In this instance if you have tankered fuel into a port and not refuelled (as currently is the case I understand for some carriers at LHR) then you don't have the gas in the fuel to start with.
Gravity feeding (in the Airbus) for a relight or continued engine operation, would only be assured once the fuel has been 'degassed' for 30 minutes. I would assume this is the same for all types.
Swedish Steve, I have not heard before that the tanks are slightly pressurised in flight. would the pressure be coming from the vent tank's NACA duct ? Interesting.