Actually, to go along with the whole "personal album" message they were insanely sending to the public, 'Alien' would have been a much better choice as a lead.
However, they were, as we all know, only thinking about Vegas and Alien isn't a song that sells an extravaganza show in Las Vegas.
I would have done things like this:
Early July - Alien 1st single;
Late September - Work Bitch 2nd single + Vegas official announcement;
Late October - Album release;
January - Perfume, right before the shows start again;
April - 4th single, again just in time for the new leg of the shows.
Why so many of you hate so much the 'Don't Cry' chorus? It seems to me someone random decided to find a flaw in this perfect song and said "Oh, the chorus is not good", then others agreed in order to hop on this bandwagon called "Let's trash Britney Jean" just because it flopped miserably.