I just looked at upcoming events in Hetalia on the archives and saw this:
"Volume 6 of the Hetalia manga is slated to be released in October 2013. (Japanese)"
A sixth manga could mean a sixth season! Perhaps there will be one after all!
EDIT (11-27-14): It's official! The 6th season is to be called Hetalia: The World Twinkle! Thank you, ShinyRainbowMario and StarShineTheAlicorn, for letting me know!
Unfortunately, we don't have a date of release yet. but as it's been stated before, I'd assume it'd come sometime in 2016 or very late 2015. If you find any info on release dates be sure to comment or note me! I check my messages often!