I don't know if there is any truth to this rumour at all. However, all the postings above are commenting on the logic of operating London-Brussels. You only have to look at the easyJet network to realise that this would not necessarily be the basis of opening a new airport.
Look at Berlin and Dortmund. Yes, there is a London link. However, both of these airports are opening up with multiple other links within Europe which don't touch the UK. e.g. Berlin - Basle, Copenhagen, a number of Spanish destinations, Athens, etc.
easyJet is not solely a UK-originating network.