As far as I can tell there is no longer an "allowFlash" attribute for the rich:fileUpload. You'll have to way until it's implemented. Maybe the upcomming 4.1 will have flashUpload or sometime next year....
I just tried the latest 4.1 Milestone release 4.1.0.M4. No luck. Bummer. Thanks for the reply.
Do you know a workaround?
I am interesting in filtering file extensions in open dialog.
We are also interested with this functionality, we already have it with RF3 aplication and would like to port to RF4.