Welcome to Hetalia: Axis Powers Answers. What would you like to know?

No clue. We'll see when we get near the end of season four's run. But the chances are pretty good.

There has been an announcement by some people on YahooAnswers and in some YouTube comments not too long ago. Since voice actors had been busy with other stuff, they won't be able to make new episodes so soon. However, there have been new character songs such as hong kong, Taiwan, Seychelles, Canada, etc. so I'm sure there will be one. Someone predicted it won't be until November 2013, but we can't so sure...

Edit: There is a Season 5.  It finished not to long ago.  Now there's going to be a Season 6 which we're all waiting for. (hopefully.)