Kdevelop 4 and kdevplatform beta5 .deb packages for Kubuntu Jaunty 9.04 are available on my backports PPA.
To install them:

• Copy the lines below and add them to your system’s software sources. (Read about installing)
  
deb http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu jaunty main
deb-src http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu jaunty main

• Import public key for my PPA:
  
  sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9D0C02D0

• Update and install package kdevelop
  
sudo apt-get update
sudo apt-get install kdevelop


EDIT:
I had some problem updating the new version, I fixed them deleting all kdevelop and kdevplatform files

find ~/.kde -name "*kdev*" | xargs rm -R


EDIT:
I still have problems with this version including some boost headers.