That really depends on the kind of bond you had with those people. If you only shared a common time or place, you'll have nothing to talk about other than a few reminiscences. If you shared something deeper, you'll be able to talk as if no time has passed.
Consider this example from Lewis' talk on philia, or love between friends.
The men in a tribe are all hunters and fighters. They get together before the hunt or the fight and talk about it. After the fact, they'll have to talk about the affair, what they did well, what they did badly, how they could do better next time, that sort of things. Each might consider the others reliable teammates, but are they truly friends?
Now, imagine if two of those men go off together and start to figure out life, the universe, and everything. They connect not as mere comrades, but as human souls. The art, science, or philosophy that they are working on together breeds a closer bond than hunting or fighting ever could.
Now comes for the real test. If you took each man and put him in a different society for about ten years using different techniques, living different lifestyles, becoming different people, then brought them back together, what would they talk about? There might be some awkward reminiscences about their hunts or fights, but little beyond that.
However, the two who formed the closer bond will be chatting away as merrily as if they had never parted. That is because the philia they shared has not changed even though the men themselves have.
