Scott Disick, Sofia Richie: Congratulations???

Scott Disick and Sofia Richie kissed passionately as they got ready to slice into a cake inscribed in frosting with the words, "Congratulations Scott and Sofia" ... and that raises some BIG questions.

The two were all over each other at a Miami restaurant Saturday night, and it clearly was not a spontaneous event. The cake and everything else about it seems like a pre-planned celebration.

Of course, the 2 things that come to mind ... engagement and pregnant. One sources tells us Scott, 34, and Sofia, 19, are not engaged. There are other possibilities. Another source says it's their announcement they are officially boyfriend and girlfriend, but we can't vouch for that.