I looked up "for sure" in my handy-dandy dictionary, and to me, it seems to mean something like 100%, and gosh, sometimes I even have difficulties determining if something that happens is 100% in the past, let alone proclaiming such for the future for something that has not yet happened.

By the way, if I said that it is 100% certain that the sun is going to come up tomorrow, I am probably going to be correct "for sure," but I doubt that my statement is actually correct and such sun coming uppity would be a 100% thingie-ma-jiggie.  #justsaying