Carina [EB03-004]

If the [When Attacking]/[On Block] effect of my "OP06-009 Shuraiya" causes it to have 6000 base power or more, does this Character gain +4000 power with its [Opponent's Turn] effect?

No, it will not. In this case, because [Shuraiya] has 6000 base power or more, you will have a Character "with 6000 base power or more", and therefore [Carina] will not gain +4000 power.