I think Foster has an excellent chance to finish in the top 10. I was going to post this after Week 1, but got busy and then forgot about it. At any rate, I have data going back to 1995 for my league. The scoring system is 6 pts for TDs (RB/WR/TE), 3 pts for TD passes, 1 pt/10 yards rushing & receiving, 1 pt/25 yards passing. No PPR. Defense is 3 for takeaways, 1 for sacks, 6 pts for all TDs, including special teams, no points allowed, other than 10 for a shutout. Based on this scoring system, I have every player since 1995 who went off in Week 1, with at least 35 points, and how they finished the season at their respective positions:
1995 -- Emmitt Smith (46 points); finished as the #1 RB
1997 -- Tim Brown (39 points); finished as the #7 WR
1998 -- Garrison Hearst (39 points); finished as the #5 RB
2000 -- Marshall Faulk (45 points); finished as the #1 RB
2001 -- Ahman Green (35 points); finished as the #3 RB
2007 -- Tony Romo (35 points); finished as the #2 QB
2008 -- Michael Turner (40 points); finished as the #2 RB
2009 -- Philadelphia Eagles (38 points); finished as the #2 D
2009 -- Adrian Peterson (43 points); finished as the #2 RB
2010 -- Arian Foster (41 points); ???
So Foster could be a one-week wonder. Take it for whatever it's worth to you, but the above numbers seem to suggest he'll be a fantasy force all year long, barring injury.