The original Sealion was supposed to happen in 1940, before North Africa or Barbarossa.
If, by some chance Germany secures NA and the Med and takes out Russia and spends a year preparing correctly and the US stays out, then a 1945 reprise of Sealion is a possibility.
Still damned near impossible (MAYBE a 1% chance of success). You literally have to replicate the mid 1944 conditions the Allies had achieved over the Channel. Naval supremacy (E-boats getting lucky against a practice aside), Air supremacy (I believe the Luftwaffe got a total of 20-30 sorties up on D-day, most of which were shot down or driven off), and enough landing craft and bombardment ships to land on at least a twenty mile frontage.
You also have the not insignificant problem that it would be the first sizable amphibious evolution for the Wehrmacht (Kriegsmarine AND Heer) against a well defended objective. Amphibious operations are a learned art, as American (and to a lesser degree, Commonwealth) operations indicate. If one compares the USMC operations at Tarawa with those at Iwo Jima or Okinawa, or the Allied effort at Normandy, the differences are stunning. Had the Allies used the tactics from Galvanic or Torch on D-Day, they would have been repulsed (this is the ONE positive from the Med campaign, the Allies did learn from each screw-up).