They will find another one after 15% rate too. The problem is not the effective rate (which is currently 12.5%) but that the companies are allowed to get away by paying 0% through the loop holes
Hilariously enough, because of all the anti-tax haven stuff, Ireland has ended up with the cleanest dirty shirt and now books lots of revenue from corporation tax.
Full disclosure: I live in Ireland and have benefited from these credits in the past (though not at present).