Very comprehensive analysis by Brian Tomasik on whether (and to what extent) the simulation argument should change our altruistic priorities. He concludes that the possibility of ancestor simulations somewhat increases the comparative importance of short-term helping relative to focusing on shaping the "far future".

Another important takeaway: 

[...] rather than answering the question “Do I live in a simulation or not?,” a perhaps better way to think about it (in line with Stuart Armstrong's anthropic decision theory) is “Given that I’m deciding for all subjectively indistinguishable copies of myself, what fraction of my copies lives in a simulation and how many total copies are there?"