They are coming……………….
Maybe he ment the black rock. He said “they” like they had come before.
Also Richard is from the black rock because when we see him making that ship the episode before the season finally. He made a ship which what looked like a light gold front sail on it
although the term “they” suggests familiarity, i feel that, on this occasion Jacob obviously refers to our heroes trapped in the 70s (well who were trapped prior to the nuclear explosion anyway). i’m not with you on your speculation – i highly doubt its anything to do with the Black Rock. The Black Rock was shown in the opening clip to serve as a parallel with Oceanic Flight 815 to suggest that Jacob is responsable for both their arrivals on the island. I do enjoy your theory about Richard though. Quite possible he did originate from the Black Rock
Some people seem to think that “they are coming” refers to the Oceanic 6. For example, the hydrogen bomb might cause them to jump 30 years in time. At least according to Lost physics… 🙂
but If it was the 1977 people why would he tell new locke about them. Its wouldn’t make sense.
Now new locke is going to try to be ready for them.