Tbh i didn't expect G4 to still have a timelimit at this point. At mentioned in this thread, i was expecting for Oda to show Luffy's next level King moves:
https://worstgen.alwaysdata.net/forum/threads/luffys-evolution-on-his-way-to-defeat-kaido.10747/
I still think it'd happen, but with the way Oda still shows Luffy's G4 drawbacks, it doesn't really make it realistic for him to gain a stronger form on top of that when he didn't even manage to remove the G4 drawbacks yet
Pretimeskip, g2 had drawbacks(stamina issues), same goes for g3(turning chibi-mode), drawbacks he removed with the timeskip(with partial g2 without turning chibi again while using g3) while learning a new mode(g4), so i thought that with the remaining timeskip training time, his experience in fighting multiple high tiers, learning an advanced level of hardening to it's maximum, it'd allow him to regulate his haki better, so that he could use G4 with little to no drawback
The only way out that Oda could find towards this is if he somehow explains that G4 drains Luffy more due to advanced haki level3 being more taxing that regular haki, but eventhen, since we're in a top tier battle now who are known to fight for days, it doesn't make sense imo that Luffy could realistically beat a top tier with such restriction
Either it'd mean that he'd gain a power-up so strong that even a top tier(weakened or not) couldn't beat him in the limited period of time of the mode(in which case, it'd signficantly diminish my top tier perspective) or he'd continuously get help to the point the top tier(s) he'd face will have to be weakened enough for his limited timelimit mode to be able finish him, which on the other hand, would completely destroy Luffy's character growth on his way to pirate king, something i don't see Oda doing
I still think Luffy will end up overshadowing everyone, especially since he already hinted at the beginning of the battle of the possibility of Luffy matching Kaido, which leads me to believe, there will be a Luffy vs Kaido chapter, but the way Oda is going with this makes you question the point of Luffy's training growth on his way to fight Kaido. Even if he gains an additional power-up mid fight(awakening or something of the sort), i'd still question myself of what is the point of G4 still having drawbacks at this stage