My own personal prognosis is that  EU tax harmonization will slow down over the next five years, at least as regards the legislative side of corporate income taxation. That is because the predictions are that the May elections of the next European Parliament will result in a substantial minority of conservative Euro-skeptic members.  This, in turn, will result in a European Commission hesitant to go too far out on a limb and ahead of the voters by enacting rules which erode one of the last remaining bastions of national sovereignty, being theright of a country to determine its own taxing rules.

That being said, there will continue to be progress made and new developments in the area of indirect taxation, especially as concerns VAT.  Plus, the European Court of Justice will continue to rule -- albeit in a haphazard way (dependant, as it is, on the cases which are brought to it) on various matters of pan-European significance and thereby continue to create an important body of EU tax jurisprudence.