I think the postponement of the "official" launch of the A350 is in order to give time for negotiation/argument with the US/WTO over launch aid rather than anything else. Clearly it is not preventing Airbus getting on with their marketing and sales activity.
If they officially launch the A350 now, an obvious question is "how much launch aid is going into financing the development?" and then it turns into an Airbus vs Boeing argument again. Might as well attempt to resolve the trade dispute first.