My picks (this is just for fun. I'm not with any potential bid teams):
2014: Columbus, OH (It's a great little town with nice convention-scale hotels which is not to far from many chapters)
2016: Baltimore, MD (Definitely a great city for tourists in a great region -- and we've surprisingly never had a national convention there. The food is GREAT)
2018: New Orleans, LA (I'm sorry.... I freaking love New Orleans and will support it until the day I die lol)
2020: Seattle, WA (Never been there and want to go
)