It would be unprecedented, but having a pitcher that just started pitching in June leading pitchers that started in April in strikeouts by season end. Strasburg pitching performances have been unreal. Strasburg is averaging about 10k a game and has the potential to throw in about 18-20 games over the course of this season. To put in perspective, four more good pitching performances gets Strasburg on the top 50 leader board for all of MLB but he'll need just two to lead NL pitchers.
Personally, I think it's a safe bet to say Strasburg will be in the top ten of all strike-out leaders by season end barring injury. Heck, if the injury bug strikes Lincecum, Haren, Oswalt, Halliday, Kershaw, Wainwright, Oswalt, Lirano, Lester and Weaver, Strasburg could be the pitching strikeout leader.
Notice...I didn't include Ubaldo in the list...Ubaldo in my opinion won't be strikeout leader this year but probably the ERA, WHIP and games won.