Hi, I have GA5, if I buy the upgrade in sale can I keep it and use it for GA6?
No. 
The currently available update can only be applied to GA versions < 5 in order to bring them up to version 5. If you already have GA 5, the update won’t work.
Ok, I was hoping it could be used like when you buy a license and activate it when the new version is released.
Thank you 
Yes, that would be nice. 
It would probably work to hold back the activation code if you updated from GA 4, for example, and take advantage of a future grace period. Owners of the latest versions are out of luck here.
That only works with new licenses, and thanks for reminding me. I think Im finally going to pick up the full GA on this sale and do just that, because I have a feeling like the C13 sale, GA6 is right around the corner…
whats your source on this?
What, that you can hang on to a download access code for a full version license and redeem it whenever you want?
How about Steinberg is the source?
No. I mean the source that GA6 is coming up?
You might want to go re-read my reply. I never said it WAS coming out and never stated anything as fact…