Yes. I ordered my CD late Friday evening before my WDW photos expired. While my WDW photos are now gone, my DLR photos are still up along with all the photos I uploaded from my own camera. And if you wanted to, you could always go back after the pics have expired and upload the PhotoPass pics to use on some of the other products if you wanted to.
The pictures in your account will all be on the CD. And until they expire, they will all be on your account. So yes, you can order other items later.
But FWIW, other photo sites make things like coffee cups, calendars, etc. You might want to seriously check out shutterfly, photoworks, etc, to see how competitive their prices are, before using photopass to get those. You'll have the pictures and the rights to use the pictures on things like that, so be sure you're not wasting money.