From what I know, it's just a rough date - and considering that Serbia still denies all the evil it has done in the wars against its neighbors, and still claims the territories of other countries in a project they now call the "Serbian world." (before Great Serbia), it would be insane to let them into the EU, especially with the problem of Kosovo and what they are trying to do in Montenegro.
I'm not that familiar with their politics vs the ex-Yugoslavian territories, but I expect it's not all nice and dandy.
And I also know that all it can take is new elections and new leadership for a change in the "official line", at least as declarations, and it may just be enough for EU.
Of course, I may be too optimistic (for EU, not for SRB), but I think that EU should become a new US and then a lot of problems would no longer exist.Keep in mind that EU is not that strong politically and it's easy to make compromises, mistakes and moves that can help only on short-term (and on long term may be pretty much a mistake).
However, back to the topic, the date doesn't even matter that much, as long as that's - more or less - the direction (EU and probably EUR). And that makes Bitcoin quite unlikely in the equation.