It's still possible to purchase Audition CS6, but I don't think that there's an upgrade path any more. Doesn't mean absolutely that there isn't though - you'd have to call to find out. I can give you a link to the purchase page though - Adobe hides it rather well...
(This has been asked about quite a lot, so I've just created an FAQ about it.)
Really must thank you! In fact I don't think I can thank you enough!! [Also, a thank you to SteveG(AudioMasters) for providing the link.]
Just a pity that the chap from Adobe that I got on the phone yesterday couldn't have offered me this option instead of the expensive Cloudy option.
It certainly allowed me to purchase 'the upgrade' - as a Download - albeit using the 23% VAT that Eire 'impose'.
But what a relief!!
Now I can get back to my dearly beloved ... !!