Looks like the chance to get an OLCI buy-up wil get slimmer after June 1st.
http://zakenreis.nl/luchtvaart/klm-veilt-upgrades/ (in Dutch)
- Service is called "upgrade yourself" and is access via "my trip on klm.com"
- Select number of flights now, will be expended during the year
- Service is designed for flights where Economy is often oversold