It's a bit late but here is another possibility without splitting the layout: you may also set the orientation value of the LinearLayout in an xml-file. Since the orientation values are integers (0: horizontal, 1: vertical) you may also use this way:
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="@integer/orientation" >
And then set/override this orientation value in xml-files:
dimens.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<integer name="orientation">1</integer> <!-- vertical //-->
</resources>
dimens-land.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<integer name="orientation">0</integer> <!-- horizontal //-->
</resources>