[UPDATE: Apparently producer Al Gough has changed his mind and wants Smallville to go 8 seasons.]
According to an interview with Now Playing magazine (warning:some coarse language there), Al Gough (executive producer of Smallville) stated in closing that he thought that the series would run seven seasons. The plan is still for the series to end with Clark putting on the suit and of course Lex gone completely to the dark side.
The producers still say there will be no flying (at least this season) and that things will get more complicated for Clark as far as pulling his super-stunts in a crowded city.
Since midway through this season we'll be at the halfway point for the series, I imagine that we'll see Lex start heading more towards evil than good and his relationship with Clark consisting of more conflict than even the illusion of friendship.