I see no good replacement candidate for the 737-300 ..
Is the 737-700 much cheaper to operate ?
They received bigger luggage binds & cockpit improvements recently.
oldest 737 are 12 (?) yrs old so should have another 10 yrs to go ..
They look good in the new livery View Large View Medium
Photo © Krzysztof Skowronski [epwa_spotters]
maybe KLM buys/leases some more of them, they are not expensive at the moment