Could the Saudi Monarchy ever be overthrown?.?

If they don't do anything wrong, no. Their power is based on a very solid foundation: $$$.

Never say never with these things - but they are well-liked and (seemingly) enjoy popular support. Not that criticism of the monarchy is brooked, but then you wouldn't try that in many countries - eg Thailand - which has a rather more turbulent history - if you knew what was good for you. So nothing anytime soon. Maybe if the oil runs out things may change. Some of us are uneasy about the link between the State and Islam - but then this seems currently more problematic in republics than monarchies across the world.

The possibility of any monarchy, parliament or president being overthrown by popular revolution has always existed. The fact that the House of Saud is one of only a handful of independent monarchies established in the Arab world in the last 110 years (with the assistance of the French and British) speaks highly of their ability to move with the times while maintaining a traditional conservative Islamic society.