burkjon: Sorry for the controversial topic, but I don't take sides here, I only care about the games.
Not going to happen.
For the two way to happen, there are two options.
Option 1 is for each participating GOG game to also include a Steam key in it. That means GOG will turn into another steam reseller, and those do not survive long. Yes, there are a couple that do, but they survive, not thrive. This option would also lead to a ton of abuse, by people buying the GOG game then passing the key to someone else, duplicating the license. A very bad choice.
Option 2 would be for GOG being able to automatically add the games to your Steam account, like Humble was doing a few years back. Steam has retired that option though, so that can no longer happen.
Your best bet would be to contact the publishers of the participating games, provide them with your GOG receipt (or account screenshot) and ask them for a Steam key. Few of them have problems giving out keys, though that does mean interacting with another human being and not an automated process. So be polite if you go that way.