Did you ever search what Shin means? I thought it was rather interesting.
I actually know what shin means (from watching anime and playing street fighter e.g Shin Shouryuken-Shin Bakunetsu screw) it means "True " which could be used for either him being actually a real uchiha (Uchiha Shin= True or Real Uchiha) instead of an experiment or him wishing to be one himself or thinking he's a real uchiha when he's not.
But kishi likes to confuse the reader (like when he made us think tobi is really madara by making him have long spiky hair like him or Itachi's true intentions) so he might have made kakashi state he's an experiment made by orochimaru to make us believe so.
Kishi will probably restore naruto to it's greatness with this new story since he finally got rid of all those OP characters (Naruto and Sasuke probably won't join the battles much) I hope he changes it to a full blown series instead of a mini spin-off because I miss the "Ninja" feel the manga used to have.
Shin can't be Sarada's brother because the other guy is his dad
We can't be sure that guy is actually an uchiha since his eyes look fake as hell to me.