The interpretation believed by scholars who believe in the possibility of non-Muslims getting into heaven is that when the Qur'an talks about Islam as the only acceptable religion, it is in the context of a question that arose during the revelation of Islam.
Along with Muslims, Christians also believe that they follow the path to salvation, the path inspired by divine Scripture; regardless of what condition that scripture might be in, they believe that they were following God's book. Similarly, Jews were thinking the same. At some places in Muslim Scripture, Jews are even encouraged to follow their Jewish laws.
The question arose that among these different interpretations of the same original divine commandments, which path would be the correct path? Amongst these varying paths it was commanded by Allah that only the path shown by Islam is the correct path. As far as this verse is concerned, it does not mention any punishment for people who follow the other alleged paths to salvation.
Regarding the Qur'an verses which mention non-Muslims "will burn in hell forever", these scholars argue that those verses are concerning only those Kuffar who directly rejected Prophet Muhammad. They argue that the only people going to Hell we can be sure of, are the ones who directly rejected the Prophets during their lifetimes. Because when a Prophet lives within a people, they have the opportunity to get answers for each and every question they might have. When all legitimate questions that a person has, get answered and still he does not believe in Allah, then he is deliberately and maliciously rejecting the truth. For this sin, the punishment is Hell (whether it is forever or temporary is a different issue).
Additionally, the Qur'an clearly says that Allah can forgive all sins except associating partners with Him. According to this verse, especially the Jews (and maybe all other people except polytheists too) stand a good chance of having all their sins forgiven.
Regarding abrogation, when it comes to subjects such as limited allowance and then prohibition of alcohol and changing of the Qibla for prayers, there is hardly any difference of opinion on the matter. But when it comes to other issues, things become much more tricky and complicated which allows for high difference of opinion, especially when it comes to the alleged abrogation of Qur'an verses by the Hadith.