Noni Madueke's arrival wasn't to replace Saka, but rather as a backup player to ease Saka's burden and fill in for him when he's injured.
I don’t think anyone will even think Madueke will replace saka, what is Madueke playing that will make him replace saka, which player will Arsenal even be signing that will replace saka for now? I don’t think there is any player, Madueke is just a backup player, and am sure they won’t be using saka frequently again, matches which they known that it won’t really be difficult for them, am sure they will bench saka and use Madueke, or maybe when Arsenal are already winning confidently, then they will bring Madueke into the match.