It's 45% of passengers who are connecting on ORK-AMS (representing around 80K passengers per year), although not all are connecting to KLM.
Maintenance of the ability to connect to KLM was one of the European Commission's conditions for the IAG takeover to go ahead. However, that doesn't mean that there has to be a formal codeshare, so while the ability to connect may be there, the ability to book a flight from Cork on the KLM website would go.
As said by EI-A330-300, KLM will know exactly how many people are connecting out of Cork and what the revenue they are getting from follow-on flights is, so they will know if it is worthwhile adding their own connection.
The only real caveat I would have is that a lot of the Cork connections are on to short-haul destinations not served from Cork, while from Dublin, the connections are predominantly to eastbound long-haul. What that means is that the yield for KLM from Cork pax will be lower than from Dublin, so the business case won't be as strong for launching it themselves.
Should they decide to launch, I would expect a Cityhopper service with a 2x daily E190 (possibly an E175 or Fokker 70 at launch).