The hill assist feature on the DSC8+ on the E87 (130i only), E90 and E92 only works with manual gearboxes. It's when you're stopped uphill, brakes on, you can just lift the clutch and you'll be rolling forward for a few seconds almost like an automatic tranny car, without applying gas yourself (as you don't need to apply gas to get started on even ground either, just lift the clutch with the right technique.)
It's not something that would keep you automatically static and not rolling back if you do not apply the brake, thus I do not think it will affect the upcoming SMG IV in any way. You will still need to apply the brake to stay static. I personally often use my slight uphill parking post so that I drive upwards into it, then hit the clutch and let the car roll back downhill a bit and adjust my final parking position, without having to change gears to reverse, so I would hate to see the SMG force you to change to R every time yo wish to go backwards. It should work like a manual in this respect.