Quote from CSR:

Thank you for contacting Blizzard Entertainment.

I have read over your current ticket and understand you will not be receiving your Collectors Edition of D3 until May 18th and are wondering if you can replace a standard key with the CE and have the Standard key released for reuse.

Yes, this would be possible. You would have to purchase a digital key at $59.99 however and when you receive your CE copy and upgrade your account the Digital key will be replaced. You will then have to contact us to have the standard digital key you purchased made available so that you can give it to someone else. We will not provide refunds for a situation like this however, we will only make the key available for you to give to someone else.

Please reply to this ticket if you have additional concerns. If you would rather speak with a representative directly, please contact Account & Technical Services. Our contact information can be found at http://blizzard.com/support/article/cs.

Regards,

Game Master Apheril
Customer Services
Blizzard Entertainment