Well once the destination of dubai becomes more developed the route probably will attract charter airlines. The only holiday company that offers a full range of holidays in dubai is Virgin Holidays with Virgin Atlantic (highly unlikley to serve CWL)
Emirates however is a airline with a large fleet on order with 45 A380(not coming to CWL) 24 773er, 10 772lr, and with 18 A340-600HGW orders on hold. (and not sure if they have A330 on order). So with this ever growing larger fleet is this really unlikley.
And with serving London heathrow and gatwick, Birmingham, Manchester and Glasgow in the UK would not an airport such as CWL really be that unlikley. With others like NCL and EDI.
PlaneMan