It looks like Google might be preparing a full holo-style Play store for Android devices. Droid-Life have unearthed a new version of the Play store, v4.0. This new version features a huge redesign to what the current Play store looks like. The current one does have some little holo styling here and there, but this new one is a fully fledged holo style app.
It looks to be a very early build because some parts of it doesn't work at all, such as the dynamic main page which would usually show you new apps, offers and recommended content in a magazine style view.
The background is now a light grey and items are presented on little white cards. Depending on the parts of the Play store you're in, the accent colour will change which is a good use of colour association.
Who knows when Google will release this new version of the Play Store, it may be at the Google I/O or even later this year when the new version of Android is released.