Some interesting history here, but no real news. According to IBM, RPG III is strictly legacy, and RPG IV must coexist with Java.
My, I'm inclined to doubt that many new systems will be written using any RPG at all. Though the developpment tools are improving, RPG itself is still a pig. My current company is a '400 shop, and our main product is in RPG III, but even we haven't written a new system in any flavour of RPG for some years. There is still plenty of maintenance and enhancement work for the RPG people, but it's strictly legacy stuff.
And if you are a '400 developer, and you don't know Java yet, then now is the time.
Some other iSeries stuff: