A lot of sci-fi tends to portray body armor in the future as very big and bulky, often designing armor so heavy that it requires engineering and power for humans to utilize it properly.
My understanding of body armor is designing it to be lighter, less bulky, and more resistant to conventional arms. The logical progression leads to bulletproof armor that is more like clothing than armor. A possible example of this was the Sardaukar from DUNE, where each soldier is covered completely by material either soft or hard. Their clear helmets ensure their vision isn't restricted, and their BDU's are flexible enough for swordfighting and heavy physical exertion without hindering movement.
Assuming this trajectory of armor improvement, how will infantry tactics change when soldiers are near invulnerable to small arms? For the sake of setting a benchmark, let's assume the US or EU comes up with a kind of BDU that is impenetrable to small arms (up to a .308 Win or equivalent). It's complicated to produce and is made of some future non-Newtonian wacky putty stuff that stops bullets. Assuming a military could equip 30% of its infantry with this armor, how would that change their warfighting doctrine and practices?
And how would rivals and non-peer forces react to such a development? If you think of failed Spec Ops operations, having those soldiers immune to small arms would have been a game changer (Operation Red Wings as an example). It would be interesting to compare, as an example, The Battle of Mogadishu and the wounds sustained by the Rangers and Delta. Would as many have died had they been wearing such armor, considering many of them died from gunshot wounds from small arms.