Well, currently EW doesn't fly long haul, they subcontract it to other companies who fly on behalf of EW. This will change in the future by letting SN operate all long haul flights for EW instead, this way the money remains in the group rather than spending it outside the group.
Eventually it could mean that we see OO- registered long haul planes from multiple locations throughout Europe, just like other airlines do it already with short haul (Easyjet, Ryanair,.. all operated planes registered outside of the country they operate from) and even long haul (Norwegian comes to mind).
I guess the Brussels Airlines brand will be kept for Belgium, maybe even indefinitely (or at least for the next 4 to 5 years, remember there's still a new logojet on the horizon) for all kinds of operations, long, mid, short haul but they'll also be marketed as EW flights (slap another codeshare on each flight). This will keep Belgium and Star Alliance happy and yet integrates SN into EW.
Not quite sure yet how they'll handle Africa expansions from outside of Belgium if they want to do so under EW, will they be marketed as SN flights rather than EW flights or are they going to gamble and hope that the EW brand will stick? I guess time will tell.
But what's not quite clear is how many backoffice jobs will be moved.