The topic title and the body text ask for two different things:
The topic title? Probably Heartlake Pet Salon. - Could reach $150 in 3 years. Other small sets have possibilities too.
Explanation - there are very few pet based sets and friends sets in general have performed well. See Heartlake Vet
Another real possibility will be a $15-20 set with exclusive minifigures or possibly a retiring minecraft set.
Exclusives? Haunted House. For greatest gross profit, in dollar value, I choose the SSD - $1000 profit easy (at least according to my review of the set), but I don't see it reaching $2000 before the Haunted House reaches $850
Explanation - Haunted House is one of a kind. It has immense display quality and great detail, it looks fantastic and isn't limited to a Halloween display like other sets. Super Star Destroyer is a massive ship and as it has already appreciated 100% in 6 months, it could be the next $2000 set, joining the Taj Mahal, the Statue of Liberty, the Eiffel Tower, the Grand Carousel, and the mothership. The Cafe Corner and the SSD are probably the only $2000 sets by 2019, if Lego is still appreciating. Edit to add - never underestimate the power of the new SW trilogy to old sets.