As expected, the EU commission has issued a report recommending to pause the enlargement process.
No speedy Balkan enlargement as EU urges reforms
EU to take more self-protecting approach to enlargement
Personally, i totally agree with the decision, the EU has gone from 15 to 27 states in a couple of years, a long pause is very much needed. The EU is already big enough to be a major player in the world anyway, and with the latest enlargement, it has reached in the East the strategic borders that it was aiming to reach. Now, the primary focus for the foreseeable future should be on strengthening the EU as it is.
We also should be very careful about the real intentions of any future member state. Poland for example pretended to be very much pro-European during accession talks, but as soon as it secured its membership, it turned around and said it was actually quite eurosceptic, pro-American and pretty much in line with the UK in thinking that the EU should be dissolved. We'll have to make sure that future members join for the right reasons and not because they want to sabotage the EU from the inside.
It would probably be prudent to pause enlargement until the EU (or a subset of the EU such as the Eurozone/Schengen states) reach federal status, which would prevent a few newcomers to jeopardize what the older members have worked hard to build since 1957.