In principle, politicians in the EU are regularly obliged to stand for re-election. Logically some lose their seats and are replaced. This is normal. Nicolas Sarkozy the French President will know for certain on the 6 of May whether he has retained the right to another 5 years in office as President..
If he is not elected there will be another President in his place. This could refresh the European Council debates particularly as Sarkozy is from the right wing and his likely successor is a Socialist, François Hollande. This is absolutely normal and permits new thinking and ideas to be expressed.
It is a pity, however, that all the Members of the European Parliament (MEP's) are elected every 5 years all on the same date. This is irrespective of whether there has been a General Election in their country. If there is a swing in National Elections, this will never be felt immediately in the EU. The European Parliament can stoically continue as before and remain aloof to the tide of change !!!
This is just another anachronism in the EU treaty, which in my opinion should be changed. European Council members should be able to work in tandem with their European MEP's who should be elected at the same time as their local national MP's.