It could work, for sure. You could even have Dr. Connors responsible for it.
You could intoduce both Carnage and a clone of Parker by Connors messing around with the little glob of symbiote that he still has in the lab. He replicates the symbiote, but it's imperfect, and it degrades and produces Carnge. However, the symbiote has held onto the memory of Parker's DNA, and the clone is growing inside the symbiote. Connors seperates the clone and the symbiote in teh lab. That leaves us with a Parker clone, and a symbiote clone that escapes and finds Kassidy or whoever. Parker and the clone team up to fight Carnage and whatever six or seven other villians they want to overload the movie with, and *poof* the clone saga has begun. You could also have Connors resenting/resisting Parker and the clones efforts to destroy "his" creation, Carnage, and using that as a way of finally intoducing Teh Lizert to the story.
I wouldn't mind it.
EDIT: I ain't saying it is the story I want to see, just saying the groundwork is already there if they want to use it.
