Well given that one of the first things Kylo said when he saw the projection of Rey was "you can't be the doing this, the effort would kill you." it seems reasonably to presume that he learned of such things from Luke. Ergo, Luke probably did indeed know what he was doing was most likely going to be fatal. Or at the very least, he accepted it as a possibility and did it anyway (because there is no "try".)
Whether one thinks that constitutes a deliberate sacrifice is largely irrelevant to my way of thinking. I mean a person who dives onto a live grenade to save their buddies does so fully expecting to be turned into pink mist in the next few seconds, even though there is the slimmest of chance that the thing is a dud and won't go off. It doesn't change the heroism of the act one way or the other.