If Oda really wanted Speed to stay as Tama's mother figure, he wouldn't have introduced a time limit to Tama's ability or made Tama instinctively go for Nami while Speed watched with a shocked face in the same chapter. He probably wouldn't have them not exchange a single line of dialog since then, while having Tama saying she wants to be like Nami. Oda already said in an SBS that he created Speed as a big sister character.
If he was serious about giving Tama parents to stay in Wano he had much better options in Hitetsu or O-Tsuru. You know, characters that aren't brainwashed and have already fed and took care of her previously. Instead, he has been ignoring those relationships and paired Tama with Speed, a brainwashed beast pirate that has already failed to take care of Tama and almost got her killed in Act 1.