From what I read Chengdu loaded well in the summer but was hopeless in the winter. Presumably it was mostly inbound tourist traffic. You wonder if it could have continued as a seasonal service but presumably that would not have attracted much corporate business travel. Might a seasonal route make sense for a leisure based airline (VS out of LGW or a Chinese carrier now that the new bilateral offers more frequencies?)
Willie Walsh had plans for BA to serve half a dozen Chinese destinations. I don't know what this means for that.
On the bright side BA seems to do well with new transatlantic routes - LHR is better situated for transfer traffic - so it would not surprise me if MSY is successful.