Weichang is too close to the coast to be trusted as China's only space launch centre.
Security asside, that part of China sees frequent Typhoons and tropical storms during the summer season, that could make launches impossible for weeks on end.
It will probably be the preferred launch site, especially for heavy load missions and/or geostationary orbit launches.
However, China will also keep JiuQuan operational, and may prefer that for military launches because of its more secluded location deep within China's hinterlands. There are good reasons why it was originally selected as the location for China's space launch centre.
Having two launch sites would also give China a much better peak launch capability in case it wants or needs to launch assets in quick succession and/or be able to pick and choose locations for time sensitive missions.