I intend on getting my 2007 Pontiac G5'* ignition switch replaced, even though it seems fine. However, since I bought the car, I've also been meaning to get a duplicate key made.

Anyone who'* had a similar repair before: should I wait until after the key cylinder is replaced to have a copy made, or will the new ignition switch be cut and programmed to take my existing key?

It will probably be a whole new cylinder made because its the general cylinder itself that'* failing. I'd wait until after, unless the cost of a new key is astronomical.

i would agree. just thinking out loud though, if you go to gm with your vin you can have a key made for it, wonder how thats going to work, they may set the ign to your old key, or at least that "number"

Ya I believe you are on track there Justin. Gm has only so many key coded tumblers.
No doubt they will want the ignition to mach the door etc locks.
They will have to set up distribution centers with complete stock of all tumblers.
Then dealers will have to order for each VIN/key number and then install.
And the big-bug question is how long is this going to take before replacements are actually getting installed into customer'* rides?

The gm dealer i use to work at. Did all the door and ignition lock keying In house the parts dept did it.

I had to dig deep to find this..It would appear no tumbler work or re-keying is necessary!
Image included from Washington Post link:
Key questions and answers about the GM recall controversy

A 0.6 cent part is causing all these issues?

sounds about right. That is what controls how hard the key is to move from one position to the next.

So, is the recall to replace the whole ignition switch, or just the detent?

I think they are only replacing the detent. I doubt they would spend that kind of money to replace the whole thing. Those things are probably $200-300 a pop.