1. Open Inkscape and configure the Document Properties (File > Document Properties or CTRL-Shift-D) to your default settings which in this case is with a Landscape orientation and I adjust the view so the page fills the screen.
2. File > Save As (CTRL-Shift-S) and navigate to:
App\Inkscape\share\templates (portable version)
c:\Program Files\Inkscape\share\templates (installed version)
and choose to replace default.svg.
3. Close Inkscape and reopen. It should open to your preferred default view now.