As it happened, this worked probably better than the Germans had any right to expect, and France fell within weeks. I think you could make a pretty decent case that even a moderately better-run French army could have stopped this offensive in its tracks, at which point Germany is up the creek and any fancy plans you might have made for a follow-on invasion of England are out the window anyways.
But you couldn't have known all that was going to happen in 1937, or 1938, or even 1939, if you were a German planner. If you fully expect that France is going to be a tough, all-consuming slog, then you're going to focus on that and leave the England plan for another day, which is precisely what happened. In retrospect it looks like a horrendous lack of planning on the part of the Germans, but really what's happened in mid-1940 is that they've just succeeded beyond all measure and now they're stuck trying to figure out what to do next.
At that point -- and that is why most people here have concluded Sea Lion is simply not plausible -- you've got an army that has never really taken amphibious warfare seriously in a large-scale, sustained way trying to improvise, in a matter of weeks, the invasion by sea of a country that happens to have the world's largest navy. For what it's worth, the British similarly let their land defences languish in the run-up to the war, and when France fell, there was a mad scramble on the British side too.