Usain Bolt, current record holder, is 22. Asafa Powell, previous record holder set the record at 23 and held it till age 26. Tim Montgomery set the record at age 27.
No, it's not too late. But to run those kind of times, you're going to need a coach. Those guys don't train themselves. You have 4 years to train for it though as it's too late to make it this year. You'll be 26 when the next Summer Games rolls around.