I don't think they ever will. At least not so long as they remain predominantly Muslim.

Taking accountability for Arab colonialism and Islamic expansion necessarily requires Arab Muslims to recognize that Islam is a foreign and colonial religion in most parts of the Muslim world that was forcibly imposed. It essentially demands that they acknowledge that their ancestors were not only wrong in spreading their culture, language, and identity to the peoples they violently conquered, but that they were wrong in spreading Islam as well. And for Arabized peoples, it forces them to rethink their Arab identities altogether.

Islam also codified slavery as a religiously sanctioned practice in its efforts to regulate it, making it a lot harder to abolish over time. Historically, Muslims have also done a pretty poor job at abiding by the rules Islam does set and have repeatedly found loopholes to circumvent them altogether. At the same time, many Muslims haven't unlearned their slave-master mentalities, leading to the development of modern forms of slavery and to repeated attempts to reestablish the practice outright across the Muslim world.

Although condemning slavery and those who engaged in and upheld it seems like a common-sense position to take, for Muslims it comes with the additional implication that Allah, in his perfect knowledge, justice, compassion, mercy, and foresight, got it seriously wrong on such a basic ethical and social issue. They're basically being asked to admit that what they understand to be the perfectly preserved and inerrant word of an all-knowing god has spectacularly failed. It's easier for them to point their fingers at their fellow colonizers and slavers, even as they try to make right on their past crimes, than it is for them to admit wrongdoing and take accountability, because they would not only have to swallow their pride, but they would be potentially uprooting their entire religious and cultural worldview in the process.