How to choose location for kitchen rough-in plumbing
Production cabinets are made in standard sizes. If you can make some general decisions about what the future kitchen layout might look like then you can forecast reasonable locations for the plumbing.
First is to decide the shape of the future kitchen. Would it be a single-wall layout, L shape, U shape, peninsula..?
In the US kitchen base cabinets are generally offered in 3-inch increments from 9 to 42 inches wide. Drawer stacks are commonly 15 or 18 inches but sometimes as narrow as 12 or as wide as 21 or 24. Ordinary box cabinets are probably most commonly 18-36 inches wide. A full size sink would usually sit above a 36 inch sink base, but because this is a secondary kitchen space may be tight and you might plan for something narrower.
You've mentioned that the cabinetry would run along an 8 foot long wall and is near a corner. Because it's a small kitchen a narrow sink of 30 inches or less may be appropriate/proportionate. My personal thought is that a sink at either end of the 8 feet would be unpleasant to use so plan on the sink base being the second cabinet from either end.
Assuming a one-wall layout I suggest the 8 foot space be divided into four cabinets: 27 inch, 30 inch sink base, 24 inch, 15 inch drawer stack. There are only a few ways to arrange these. I'd put the 27 inch in the corner and the 30 inch sink base beside it. Then the sink would be centered about 42 inches from the corner and the plumbing could be roughed in near there. You'd still have some flexibility to go 3 inches wider or narrower with that first cabinet as well as with the sink base.