2001-present Albert Pujols .331, 412
2003-present Miguel Cabrera .313, 252
Helton and Guerrero are likely close enough to the end of their careers to be safe from falling below .310 and Pujols will probably finish well about .320 even if he declined late in his career.
For various reasons (DH, Coors Field, performing enhancing drugs), Pujols is the only lock to be in the Hall of Fame of anyone on the list not already in, although Miguel Cabera is on the right track if he can stay out of trouble. If enough people are excluded from the Hall because of steroids, Edgar Martinez's DH issue might seem like not as big of a deal and he can come up from the 36% he's gotten his first two years.
Vladimir Guerrero proved last year that he has something left in the tank, but he needs a few more good years to be in serious consideration for the Hall.