Well, Islam will vacate the 155 belt then, I assume?
Btw, he should fight his way through the rankings, not a straight title shot. If Topuria did nothing at LW, as such was Islam's argument, why does Islam get to go straight for the belt? Because he had more defenses? If so, that falls flat as Islam Makhachev called for the Leon fight as soon as he beat Volkanovski 1, in his first title defense (so Islam never cared about jumping straight to the title of the next division unless the guy was Topuria, whom he fears). If he doesn't want to have the commitment of making 155 anymore, because he weighs around 180lb and fights in LW around ~175lb on night's day, i.e, a very big LW that gets up to ~ 20 lb the division weight during day's night.... Then he would vacate the belt. But no champ champ unless he makes through the rankings. What has he done in 170? Nothing.
His extreme cut and weight gain is partially the reason he dominated at LW, unless he faces an opponent who's very well rounded and Islam can't grow much from [the weigh] in to the [night of the fight]. That's why his fight vs Volk 1 was a tough one, because Islam was smaller than he normally would want to be in LW — in Australia, the time between the weigh in and the actual match is way shorter, so Islam fought closer to an actual LW there. He didn't that weight advantage he was used to. Plus, he was against someone from the lower category but who's also big for FW (Volk)... And as a general rule of thumb, the lower the category, the more skilled they are. In Abu Dhabi, that time between the weigh in and the fight night is extended; that's why Islam looked way bigger in the second fight vs Volk, who by the way was there on a 2 weeks short notice.
Topuria weighs the almost the same as Islam, according to the sources we have. He is also ~175lb and is expected to have his optimal fighting weight just at ~173 lb in LW at the night of the fight. Islam saw how he KO'd a Volkanovski whom, under the same conditions, gave him his toughest match up and knows that buffing himself a little over his weight is a way easier fight than fighting someone his size but who's well rounded and a huge talent. Illia Topuria.... First guy to call out Islam and Khabib, openly mock them. Say he could beat Islam and that Islam could choose the way he'd like to be beat... But Islam knowing that fight would get way more $, unlike him vs Jack, conceded to Topuria's provocations and wooofff, did want no piece of him, since even tho him vs Jack is not nearly as $, it's a way easier match for him, as Topuria has Islam's number.
Islam's whole "I'll defend it against anyone" was a moment of him pretending to be as brave as Alex Pereira, sadly.