Sure hope it'll be Monday, 'cause the Garritan website apparently states "February".

Well, that could work out, since Monday is February 1st.
It does seem very odd that Make Music and Garritan pages don't say much at all about GPO5.
Ah, fret_man.... I guessed as much after trying to find it for sale in the US.
 
I didn't see anything that required my serial # to qualify for the upgrade price. I'm sure I'll need it later, but perhaps I misunderstood Sid.
Michael

It looks like the release has been delayed. It's saying mid Feb instead of Feb 1st. That's a bit anooying, but hopefully everything is ok and it won't take too long to be released.

pentimentosound
I didn't see anything that required my serial # to qualify for the upgrade price. I'm sure I'll need it later, but perhaps I misunderstood Sid.
Michael

In the Time&Space order confirmation email they asked me for my serial.

Where are you seeing this release news?
@Fleer     It seems very odd that I didn't get asked that. I was ready for it, too. LOL    
I'd copied my serial and then it never came up. I created an account and bought the upgrade.
Oh well.
Michael

Time&Space now also states 'mid-February'.
Pentimento, his is what they wrote in that confirmation letter:
"Thank you for purchasing Garritan Personal Orchestra 5 UPGRADE (Download) (GPO5UP-120) from Time+Space.
Please note that this product is not due for release until 1st February 2016 so your serial number will be emailed to you as soon as we receive them from Garritan/Make Music.
To save time, please send us your previous Garritan GPO4 serial number. Please email us via websales@timespace.com or simply reply to this email."
 

Ah thanks, Fleer. I just emailed them and will wait to send my serial # when they respond.
Maybe Garritan has been hanging out with IK! LOL
I certainly have lots to enjoy while I'm waiting.
Michael

pentimentosound
    It seems very odd that I didn't get asked that. I was ready for it, too. LOL    
I'd copied my serial and then it never came up. I created an account and bought the upgrade.
Oh well.
Michael

You should have received two emails from Time+Space after your purchase.
 
One was the order confirmation, and the other, the instructions for sending in your serial.  For the latter, the subject line was "Garritan Personal Orchestra 5 UPGRADE (Download) - Serial Number / Activation Code".
 
Edit...Never mind, I just saw Fleer's helpful post above. 

Just as Fleer said!

Interesting... in that second email from T+S I have this: "For validation, you must enter your Upgrade serial into the same Garritan user account as your previous GPO4 registration".   IOW, I would validate at Garritan.