Michael Young: 3000 H (2085 H, 35 yrs)
Paul Konerko: 500 Home HR (398 HR, 36 yrs)
Juan Pierre: 700 SB (or close to it) (557 SB, 34 yrs)
Here are 3 players that are thought of as very good, but probably not Hall of Fame yet. Of the 3, the only milestone that would make it a near-certainty that they would get into the Hall would probably be 3000 hits for Michael Young. It is not clear how home runs will be treated after the steroid era inflated, but 500 HR would still be a great achievement for Konerko.
Juan Pierre is theoretically still in the hunt for 3000 hits too (2032 H), but his hit totals and batting average are down from his 2003-2007 heyday. He is currently tied for 25th all time in SB, but with only 101 more he would move into 13th all time. This seems likely if he can stay healthy, and 700 would put him at #11 (between Honus Wager and Joe Morgan)
It is possible that they will achieve these milestones with room to spare, but it seems unlikely. There are some players who reached these milestones in their 40's (Paul Molitor, Randy Johnson), but it is rare. Players often start wearing down quickly around 40, so there is not a lot of time for these three players. For right now, they are playing at a high level, which makes these milestones very possible in the years ahead.