So far i have a USB drive.
Partition into 2
1 partition is a CCC backup .. dont know if its bootable though?
2nd partition is a fresh time machine back up
is this sufficient?
If yes how do i then wipe the mac and then how do i transfer contents to the new mac ..
Your plan can work but it has the weakness that all your stuff is tied to one physical device that if damaged takes all your data with it.
Start by making the drive GUID partition scheme then create two HFS+ partitions. One for Time Machine and one for the CCC backup. The CCC backup partition doesn't need to be as big as your Macintosh HD as a lot of log files and other cruft are not copied by CCC.
You can then make a fresh new TM backup to the second partition along with a bootable clone using CCC. At this point you can test the bootable clone by holding option while your MBA is booting with your USB drive plugged in.
Once you're convinced you have at least 2 backups that work, you can go ahead and wipe your MBA. There are several ways to do this. One is to do a "wipe and install" and simply not migrate any data. Another is to create a new admin account, then delete your old home folder. This leaves 3rd party applications and other cruft lying around but it is the fastest way to wipe a Mac.
When your new machine arrives, you can plug in your USB HDD and "migrate" from your fresh TM backup. If something goes wrong, you also have the bootable CCC clone sitting there on the same drive and you can either migrate from that or boot from it on your new machine.
Keep in mind that USB drives cost less than $90 and it's well worth having an independent second backup of all your stuff if you still intend to allow the MBA to go before you have the new mini in your hands.
If you only have a few gig of files that you "really care about", take the time to copy them up to a dropbox or box.net online folder so they are backed up a second time. Running a "fresh" TM backup can take 6 hours or more depending on how much you are backing up. Running a CCC clone can take a few hours as well. Uploading several gig of files to box.net or another online backup site can also take several hours depending on your internet connection. Bottom line: Get started now if you still intend to let that MBA go as of tomorrow!