I don't think either Luke or Jessica are Skrulls, and I'll tell you why.
Baby Cage is misdirection, there to throw everyone off. Baby Cage is there to make you think "either Luke or Jessica are Skrulls". But niether of them have been acting out of character at all. They're both as cool as ever. Baby Cage is there so that they will accuse each other of being Skrulls. Baby Cage is there to break the team up, which is what the Skrulls want. So that means someone else was in a position to take the real baby, and swap the baby for a Skrull. Who? Maybe Spider-Woman. But who would be in an even better position? Wong.
I think the following people are Skrulls...
Baby Cage
That lizard guy whats his name from the savage land.
Spider-Woman
Captain Marvel
Sentry?
Wong
Clint pre-hom. The current one is the real Clint.
The Punisher has been acting very strangely since his return to 616.
Miriam Sharpe
Maria Hill- Or at least, put in place by the Skrulls.
Sentinel squad O.N.E, or one of the leaders that put O.N.E where they are is a Skrull. O.N.E is waiting for the right time to attack to wipe out what is left of the mutants.
The Skrulls have been behind the breakout, obviously. Not directly behind Civil War, but helped move it along. Magneto being missing. The next time Mags shows up, hell probably be a Skrull. The corruption of SHIELD and HYDRA. I bet they turn out to be involved in sentinel squat O.N.E somehow.