I have some news.
I went to the official website, and I found this :
３月１１日第４８話をもってアニメ「ヘタリア Ｗorld Ｓeries」全話の
"The 48th episode will be the last, thank you for your support."
Translation by lost_hitsu :
With the 48th episode aired on 11.3., the distribution of the anime Hetalia World Series is completed FOR THE TIME BEING. (the keyword being hitomazu ひとまず - for a while, for a time, for the present) However, as a thanks for your support, we are secretly working on episode/episodes, (the plural is vague in Japanese) other than the 48 distributed ones!
• Nordic Extra-Episode for March 25. Pictures :
Plot summary :
Iceland has a little kick-the-cat to make a DNA test!
Read the letter written by the DNA test results, four members of Northern Europe.
There are a result that was written by brothers how Iceland and Norway!
(Translation by Google)
• DVD vol.5 cover :
That all, bye o/
Why they're speaking of the Nordic episode as a "Extra Episode" ?!
"『ヘタリア Ｗorld Ｓeries』エクストラエピソード 第１弾 北欧５エピソード!!!"
("Hetalia World Series" Extra-Episode first step : Nordic Episode !!!)
This means the 47th/48th episode is a other animated strip ?
Episode 46 : February 25
Episode 47 : March 4
Episode 48 : March 11
Nordic Extra-Episode first step : March 25
Edit 3 : I forgot to translate the title, who says all orz
『ヘタリア Ｗorld Ｓeries』エクストラエピソード春休みに配信決定!!!
"[World Series] decision delivered Hetalia Extra-Episode spring break!" (Google)
So, they taking a break.