if i had to guess, i'd say he does like like a bunch of rapid strikes to an enemy and that bar shows how many are left.
It's a 1 hit. The energy bar is just a nod to the FE series, I didn't really notice it when I was watching some guy playing it, but it had no overbearing affect on the FS other than to look nice. It's like in the FE games, a critical hit took off a good portion of your HP, if not all of it. Why not show that this is a OHKO by showing HP (for aesthetics) and knocking it all the way down to 0 to show an OHKO.
Thats a distinct possibility, actually. Now that you mention it, the attack in that picture does remind me of his f-tilt.
So essentially this picture only really tells us what color he glows when he gets the smash ball. Well, hopefully we'll get some images or videos of it soon - everyone else is (Falco, Wolf, Ganondorf, Game & Watch, Captain Falcon, Ness...).
Zevox
To copy pasta myself from 4chan:
So, I tried to image cap as many new final smashes as I could, then ***got leechers came onto the stream when Captain Falcon was about to do his. So, since the stream is now dead, I thought I'd post the 5 Final Smashes I saw (that weren't on the dojo)
Marth - Critical Hit, looks like a OHKO. It was training mode and Ike had 0% before the final smash started.
G&W - Becomes Cthulhu, too laggy to see effects
Ganondorf - Turns into Ganon, sweeps everybody off the screen.
Wolf - Landmaster
Jigglypuff - Inflates and pushes people off
Captain Falcon - **** the ***gots who came on when he was about to do his final smash.
http://img524.imageshack.us/img524/1923/finalsmashesjx0.jpg