The way I understand it, the various parts of the EU do not have an unanimous view on this though:
The German government is pursuing a softer line, because they would prefer the UK not to leave at all, as it has been its most important ally with regards to fiscal policy (both Germany and the UK like austerity and all that crap). Not completely sure about the Eastern European and Baltic states, but they're on the German side afaik (which is also why the image of Angela Merkel, Eternal God Empress of Europe, is wrong; there are a lot of smaller member states sharing Germany's goals and outlook).
France and Italy, however, would prefer an EU with a loosened fiscal policy, because their economies aren't so hot at the moment, so they're already pushing the UK to get on with it. A Brexit would actually strengthen their position within the remaining union.
And the European Commission is, of course, also pushing for the UK to hurry up and make a definite decision, because a lengthened period of uncertainty also hurts the European Union (though not as bad as the UK, of course, which is kind of the rule of thumb for this entire mess: Whatever happens, both sides will get hurt; however, it will hurt the UK so much more than the rest of the EU).
Anyway, it's safe to assume that come September and/or as soon as a new PM and a Cabinet are in place, pressure will be mounting up from all sides within the EU. Trying to stall invoking Article 50 well into 2017 won't go down well, not even with Germany and its allies.