So we have two factors that could lower Lillard's averages:
1 - Scouting. Word's out now. He might not get a double-team because of passing concerns (open guy and all that) but he'll get every team's Wesley Matthew up against him (BTW, I hope they put Matthews and Lillard on opposite teams so he has to play against that all the time in practice). Gameplans will focus on him a little more. No more open three pointers, no more easy bounce passes, or wide open lanes.
2 - Fatigue. He's playing bigtime minutes (38+) and will hit the rookie wall halfway through the season. Shooting percentags go down, passes get sloppy... he won't turn into Nolan Smith, but he could drop significantly in output.
At the same time, there are two factors countering these:
1 - Lillard's used to it. He's been the focus of every team's best two players in a constant double team for YEARS now. Portland's starters are good enough that teams can't leave any one player open (even Hickson) for more than a second or two, preventing Lillard from being constantly doubled.
2 - Lillard's mentally tough. He plays the game one possession at a time. He has been the leader of a small-college team, and knows what it means to be relied upon even when tired after playing a ton of minutes. The rookie wall will hit, but he'll power through it.
So, that said, I think Lillard *can* maintain the bulk of his performance as it stands today (21pts/9ast/4reb): I predict 20.0 PPG / 8.0 APG / 3.0 RPG in 37 minutes per game (Ronnie Price will let Lillard play a little less). Also, ROY.