By Balazs Koranyi and Francesco Canepa FRANKFURT (Reuters) – The European Central Bank is all but certain to keep policy unchanged on Thursday but may have to acknowledge that inflation could stay high for longer than it had projected, a signal that may be taken by some as a hint at a faster exit from stimulus. Having extended support measures only in December, any policy change now would be premature. Yet inflation has consistently exceeded the ECB’s forecasts, piling pressure on policymakers to fine-tune their increasingly questioned narrative that rapid price growth is merely temporary. The…