Bug, feature request, or proposal:

Feature request

What is the expected behavior?

<md-select [floatingPlaceholder]:boolean >
<md-option ... >
</md-select>
or
<md-input-container [floatingPlaceholder]:boolean>
<md-select ...>
<md-option ... >
</md-select>
</md-input-container>

What is the current behavior?

not support

What is the use-case or motivation for changing an existing behavior?

Input elements can have floating or non-floating placeholder .Select can be use with input elements.
Select should have floating or non-floating placeholder.Similar to

Which versions of Angular, Material, OS, browsers are affected?

Material2 v2.0.0-beta
Angular 2.4.1