dal4fsu: Anyone have an answer for this?
I'd have to assume that you won't get something for nothing, whatever edition you bought a key for is what will be added to your account. The standard editions still show as what they are in the Steam library, so it's not as if they are entirely removed from the service, however I can't see my tactical pack or explosive pack DLC listed now. I think it's just the version upgrades and DLC that have been removed from the store front, and I think it's done purely so that the cheap option is gone and upgrades have to pay the highest price possible.
Contact GMG (or whoever the your retailer is) and ask them to be sure?
I guess if you don't want the DC (because of the bugs and glitches) or just want Missing Link/Explosive Pack/Tactical Pack) it will still be possible to buy remaining keys available from the likes of GMG. If you do want the DC, the sensible thing to do would probably be to return unregistered keys if you can, citing the removal of upgrades as an option and just get a cheap copy of the DC.
The DC was £3.75 (75% off) in the Steam flash sale, so I guess $3-$5 US allowing for regional price gouge that the UK is subject to on Steam.