How would a decisive Jutland change cruisers?

Would a decisive Jutland and much larger capital ships make 6- and 8-inch cruisers look too weak?

Probably; cruisers might move toward 9.2- or 9.4-inch guns, while 10- or 12-inch weapons would come too close to creating another capital-ship category.

Cruiser guns would probably grow, though the category would still need limits. A 9.2- or 9.4-inch weapon is a plausible response to a capital-ship world dominated by 16.5-inch guns. Allowing cruisers to reach 10 or 12 inches would blur the boundary with capital ships and undermine the treaty category. A different battleship baseline would therefore propagate downward into cruiser definitions and naval arms-control rules.