Newcastle is a great town, they have a beautiful stadium and many fans, they deserve a better team than this Ritchie-Lascelles-Longstaff-Joelinton nightmare.
I don't know how serious the Saudis are but either way they will need a few years to be competitive. City's first signings after takeover were better players of midtable PL-teams(Santa Cruz, Lescott, Barry, Given) or secondary players from top sides(Bridge, SWP, Robinho, Vieira). I can see Castle will follow same footsteps.