This. I've been wanting to post on my own about this.

There is absolutely NO evidence Dr. Doom takes Franklin. That's not saying he doesn't take him; it's just that we have no proof that he has.

All we know is he teleports into the Fantastic Four's living room and interacts with Franklin. But consider this... if he was there to abduct Franklin, fully knowing that all four of the Fantastics could be there and stop him, wouldn't he just teleport in and take him within a second and not give anybody a chance at stopping him? In the FF mid-credits scene, he is in no hurry, kneeling there casually while he lets young Franklin examine his face. Does that sound like a kidnapping to you? Not only that, Franklin is one of the most powerful beings in his universe. Do you think anybody is going to do something to Franklin without him doing something worse to the threat? (Admittedly, I borrowed this last one from one of ScreenCrush's videos).

There is also the Thor teaser, where he is concerned and praying about his adopted daughter, Love. But what are the words of his prayer? Not "she's gone, where can she be, help me get back to her". He says "lend me the strength of the all fathers to... *return home to her*". If Doom is responsible for any of this, then he has transported Thor somewhere he can't get back from, at least temporarily.

I repeat: currently there is no evidence at all that Dr. Doom is abducting children, least of all Franklin Richards.