Like I said:
Basically, all Christians agree on this matter fundamentally (from all the answers that I have heard). It's just all about how you define OSAS.
The ones who fall away, faithman says they are false believers. Then webmaster says the writer of Hebrews mentions the word "us" therefore he is referring to himself. But faithman can just say "Us" refers to the true believers who will not fall away....blah, blah, blah. Let us stop arguing on this issue. We all believe that there will be some who accept Christ as their Savior and follow Him, and there will be those that won't, and there will be those that will be wolves in sheeps clothing. The only ones that will be saved are those who stick with Christ. All the specifics, only God can judge.