It's official: The Pilot Con-20 and Con-50 converters have been discontinued in favor of the Con-40
A few folks will be sad to see the Con-20 converters go away. They haven't come stock with the pens in years but have been available to order individually. The press plate design makes them easy to handle and can be manipulated with one hand in your ink bottle, keeping the other hand free with a tissue for clean up.
The bigger change will be about the Con-50. And by bigger I mean smaller and by smaller I'm referring to the ink capacity. The Con-40 is a similar twist converter with an agitation system built in to prevent airlock and keep the ink from clinging to the inside of the barrel which should help you get that last little bit of writing done before needing to refill. However, John measured the ink capacity and the Con-40 falls short at 0.4 ml verses the Con-50's 0.5 ml.
For fans of the old style converters we do have a supply that should hold for awhile.
But when they're gone, they're gone.