To my surprise I couldn't find a short and clear answer for this question.
Is WAP/WML still relevant for todays mobile web/app development?
Regards, Milanko
WML is obsolete, and only used by a very small (<5%, maybe less) of active mobile devices. WAP 1.0 is similarly obsolete, but WAP 2.0 is still very much alive and kicking. 2.0 specifies XHTML Mobile Profile as its markup, which is a cut down version of full XHTML.
Crudely put, WAP 2.0 is really just a specified combo of HTTP and XHTML Mobile Profile.
You can forget WML, though, unless you really need to support Nokia 7110-type phones still.
Generally, users with WML devices, e.g. older devices, usually accept that they cannot have the same things that other devices with color screens etc can and their expectations are lower.
So you will not be missing out on users that actively expect your site to work on their device. If you do support them, then it's an added advantage, but other requirements will probably force them to upgrade their device as soon as they can.
来源：https://stackoverflow.com/questions/6465898/wap-wml-still-relevant-in-2011