Yes, you will definitely get some staining. Frankly I don't bother with sunning all the time, in my experience the stains do fade with time and washing, and when I'm about to put away a size that is now too small or am selling my diapers I sun them so they are nice and white then.
Something to try is doing a rinse before you wash them. So I do a cold rinse with nothing in it, followed by a hot wash with detergent. I think the cold water helps to not set the stains and rinsing them first gets some of the pee/poop out of the diapers before they get set in with the hot water. Also, once you are feeding your baby solids (not for a while yet, I know) I recommend getting a diaper sprayer. It lets you spray the poop off the diaper and into the toilet so they clean better and stain less. If you want to try it now too, I'm sure you could if you're feeling dedicated, though most don't bother.
Agree on more pre-rinsing and/or more frequent pre-rinsing. We pre-rinse every day but sometimes save them in a laundry basket and do the wash the next day. That way things don't get as dried on and the diapers wash out better.
If you have hard water which can increase staining I also suggest using Calgon water softener in the wash. It makes a big difference for us. Unfortunately I am not able to find it in any stores around here so we have to order it online.
Cold rinse, 60degree wash, I use ecoegg with a scoop of oxygen bleach, but breast fed poo stains cab take 2-3 washes to come out, or hang them near a window inside helps as well, if you can't get them out in the sun.