With so many figures in the pipeline, even Dwight has mentioned its hard to remember which year is getting which upcoming figure. So maybe 4 isn't an exact number. It could have been an "at least 4" type of comment.
I can see them dragging their feet a bit with the original GotG, as they're likely to focus on the more current version the movies are based on. I'm not sure the team is popular enough to warrant a boxed set either.
I see the Invaders getting a boxed set. Didn't someone say they had plans for one and it got pushed back? With Cap being so popular these days, I can see a FA version being in a boxed set. Hasbro obviously has some love for Union Jack, so I think there will be another figure of him soonish. Bucky. Human Torch. The last classic Namor hung around, so I can see them packing into a 2pk or boxed set to help sell him again. So: Cap, Bucky, Human Torch, Namor, and Union Jack. Obviously Toro could replace UJ, but I'm not sure if they'd just put Toro on a teen body and not worry about any sculpted flame detail. Maybe they put Toro in the boxed set and Union Jack would just be a standalone release.