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.
Madueke will be a force for good, that's for sure. Bukayo Saka didn't quite live up to expectations last year. Furthermore, he suffered an injury, which affected Arsenal significantly. I think Madueke, along with Saka, will be the player who will shoulder Arsenal's goalscoring burden. I don't know which one will be in the starting lineup and which on the bench; perhaps the manager will want to use both. We'll see how the tactics he implements come the season. He'll be expected to recoup the transfer fee, and we'll see how he impacts Arsenal.