As far as Ive heard during Live Letter's and Interviews it will be out with the launch of Heavensward. The new client may take time to download but dont worry, I doubt the servers will be up for some time during the maintenance. If you have a decent connection speed you should have time enough to download it all.
Also, if I'm reading the JP blog correctly (where these screenshots were posted) the upcoming benchmark will have DX11 support as well to test it out.
(Would be great if someone whose Japanese is better than mine could confirm that for me)
Source JP Blog: "4月下旬に公開するベンチマークでは、DirectX 11版も試す事ができますので、お楽しみに~。"
