Research progress and lack of soldier benefits

I just expect that there will be more research like ‘better penetration for all weapons’, ‘discovery of ammo that shreds armor bettter than current’, ‘ammo which causes severe bleeding’ (as someone mentioned) but we still will use thoase basic rifles we got on the start of campaign. Of course there will be whole weaponry of factions with different stats, but will it be better? - maybe after some upgrades but not entire replacent of old weapons with new ones (from next ‘tier’).