"On the floor" was the comeback she needed in 2011 and i am pretty sure that this single will rock and be a big hit in Europe and the US again. She will perform it on "American Idol" finale for sure in May and present the music video there. This song needs to take off on the radio first, but they seem to be very sure that this song becomes a hit. She is also filming a music video for "Follow the leader", a duet with Wisin Y Yandel from their new album.
But guys - one thing: She never said that this single is the first from a "Greatest Hits" album on Twitter or Facebook or anywhere. Maybe she releases a full new album under Def Jam? They are well known for "new album each year" (see Rihanna) and she didn't mention a "Greatest Hits" album in 2012.

Been on UKMIX Big Brother 2 in 2009 and did my own game "The Abandoned Village" in late 2009!