Airbus have around 350 outstanding A330 orders, production rates have been increased in order to meet demand. Airlines ordered 97 gross (83 net) from Jan - Nov last year.
Whilst it is true that the A350 is on the horizon, it would be a few more years before a tanker version could ever be developed and supplied. I'm sure the RAF have reached the point that the VC10's can't be kept in the air for much longer.
Look on the bright side, its the 1st time that the RAF have ever operated a new tanker, all the predecessors have been other peoples cast offs.