We'll see. Entry into the EU does not guarantee replacement of the former national currency with the euro. Hungary, for example, has been an EU member for nearly a year and it will be at least another year before the euro is introduced, provided that Hungary keeps abreast of the economic conditions required (google "Maastricht criteria" for more info.)
the Romanian economy is growing but is still light years behind Hungary's, and I doubt we'll be seeing the euro introduced there anytime soon.