Ideally???
By Clarks request Martian Manhunter takes a deep look into his mind/past and then takes of on a journey to mind wipe everyone Clark has come across that stands a chance of recognizing him once he puts on the suit.
This of course includes the ones at the Daily Planet as well as Lex and Lois.
Season 10 of Smallville is renamed Metropolis and we finally see SUPERMAN.
For the last season the shows budget is HEAVILY increased and they do justice to the classic imagery a show about superman requires.
In past seasons the confrontations between Clark and the villains usually took place in remote areas or at night where no one saw Clark use his abilities, whereas now the battles will take place in broad daylight in the middle of Metropolis for everyone to see, and Clark/Superman will have to deal with this, for better or worse, as people will eventually get tired of these super-powered people causing such extreme damages to the city, which will take a somewhat toll on Clark.
Perry and Jimmy will be introduced into the show, Clark is by now a professional reporter and we follow him as he and Lois do their investigations throughout the city while Superman himself will deal with the season bad guy which will be non other than the only major villain left he still hasn't encountered on Smallville, Darkseid. Through out the season he will face many smaller villains led by Darkseid to test the limits of his physicality to see just what kind of obstacle this Superman will be to his plans of World domination. Lex will of course be a major part of the season as he finds himself fascinated by this incredible being, but is also overcome by a compulsion to destroy him for obvious reasons, which will eventually lead into a major fight.
Season 10 finishes off with what is the most fantastic series finale ever with Superman taking on Darkseid by defeating his army and kicking his rocky ass back to where he came from.
He takes a final flight through the clouds, smiles at the camera Chris Reeve style and cut to Black.
Or... at least something like that, as this is only a rough idea I just came up with.
I know this will never happen, but a guy can dream can't he?