I don't have any knowledge of many people getting merits anymore, so I don't think they will be in AG3. I do remember someone posting that they will not be there, but I forget who that was.
Not exactly the same as it is now, but they are replacing it with the reputation system. Basically you'll be able to vote up things that you like in the forums and in game comments, and the people will receive reputation points.
I really like merits and i got one only a few days ago and it really pushed me forward to start being more active on AG, it is a shame that they are going but the new idea seems good too. Although you do find some stupid people that like to vote really short things like 'this game sucks.' and 'cool.' So it will be very judgmental and you need players that want people to do well on Armor Games e.g.GhostOfMatrix, knight_34, Pazx, nichodemus and all the moderators. So i guess we will just have to wait and see what it will be like...
