In the writer left page is usually followed by a right page and vice versa.
Therefore the 'next style' of stype 'left page' should be 'right page' while the
next style of 'right page' should be 'left page'.
Currently 'left page' is followed by 'left page' and 'right page' is followed
by 'right page', although it seems to be rather uncommon that one only wants to
create left or right pages.

Steps to reporduce:
1) Create a new writer document and set the page style to Left page.
2) Insert a page break and notice that next page created has left page style
associated.