eBay's enforcement commences on July 27, so they will fail listings of that date if someone attempts to post/relist them without the new item conditions (for the categories they apply to). The note I posted above is to alert people to pay attention to items that will relist and make sure those have the item condition updated. You are correct that listing posted from saved will fail after the 27th if the item condition does not meet eBay's requirement.
You can change the item condition for saved listings but if you want to revise live listings, you will need to that thru eBay. We don't have support for changing live listings yet, because eBay has is not enforcing changes to GTC listings yet.
Yes, GTC listings will not require the new item conditions until 2011. As far as I have seen, eBay has not yet stated exactly when they will do this.
Hope this helps.