Saudia was forced to keep a portion of its 737-200 fleet operational to serve smaller airports within the Kingdom that could not handle the MD
-90 due to its weight bearing limits on runways and taxiways.
Several airports have been upgraded in the last few years to allow MD
-90 operations. At some point I presume either the remainder of airports will be upgraded or service will cease unless Saudia gets smaller equipment.
There was a proposal a few years back to acquire Dash-8 aircraft, however nothing came of the proposal.