On 24 June 2015, the EPO’s Select Committee decided to adopt the 'True Top 4' proposal. Under the True Top 4 proposal the UP renewal fees will correspond to the total sum of the renewal fees currently paid for the four most frequently validated countries (Germany, France, UK and the Netherlands). See http://www.epo.org/news-issues/news/2015/20150624.html
The treaty setting up the UP is yet to be ratified, and significant features of the system still need to be settled. We will keep you posted as the situation evolves.