I after doing a proper research i am confident i can  upgrade to CUCM 7 directly.

Upgrade steps i found out...

"      Run BARS, and take full backup from the call manager 4.2.
"      Take the Background images, Ring tones, and the MOH to your local disk.
"      Take all phone types configuration through BAT.
"      Determining Registration Counts By RTMT.
o      Number of Phones on Publisher =
o      Number of Phones on Subscriber =
o      Number of Gateways =
o      Number of users =
o      Number of Route Pattern =
o      Number of Translation Pattern =
o      Number of CTI Route Point =
o      Number of CTI Ports =
"      Check the Services, which are running and which are not.
"      Take the Servers Names
"      Connect all the phones in the site to the System and be sure that all of them are registered.
"      Add 50 phones 7970, 7961, 7962, 7965, 7941, 7942, 7945, 7906 with dummy MAC(for licenses) Addresses.
"      Take the DHCP Backup if you have
"      Make sure that power should not go down.
"      You have to have FTP server on your PC.
"      Run the DMA and take Backup and don t make any configuration during the backup don t make any configuration after the DMA..
"      Check that all the Backups on your hard drive.
"      Check if all the phones will register with the subscriber if you disconnect the publisher before proceed with the upgrade.
"      Run the Upgrade Assistant Utility on the publisher first then the subscriber, don t run it on both at the same time. If there is no problems continue to the next step if yes solve it then run the utility again then continue.
"      Insert the upgrade DVD in the Publisher and restart the server.
"      Proceed with the steps.
"      After the upgrade check the licensing report.
"      Return the Background images to the TFTP and the MOH to the MOH files.
"      Configure the DHCP on the Publisher Server.
"      Upload the Servers license.
"      Run the services and let all the phones to be register with the Publisher and check the stability of the system. All the features should be work before upgrade the Subscriber.
"      Upgrade the Subscriber with same procedure of the Publisher but don t select it as the first node.
"      After Subscriber upgrade check the replication and check if the phones will register with it.
"      Make final tuning.

Hope the above info helps anyone trying to do the same..