Don't buy it.
Perhaps he could have jumped, but I don't think Lukaku did anything wrong short of being guilty of trying to chase the ball down, and I try not to judge people based on counter-factuals.
I don't see anything in that which leads me to believe that he went out of his way to harm Lloris, and in fact in replays that I saw during the game he was immediately motioning for help from the medics, and didn't attempt chase down the loose ball after Lloris got knocked out and lost the ball.
It would be one thing if Lukaku had noticeably dropped his knee unnaturally, but all he appears to do is to attempt to chase the ball down, which is exactly what a forward is expected to do.
How often is a keeper diving for the ball at the feet of a forward? Keepers miss or flub dives for the ball like that all the time, leaving the forward with the net wide open. It isn't Lukaku's job to assume the worst and to pull out of every run just because the opposing keeper looks to have beaten him to the ball and is diving at his feet, it is his job to assume that if the opposing keeper flubs it then it's an easy goal, and perhaps three points in the bag.