Ji Gunjayish bilkul hai!
The Christians and Jews which the Ayaah talks about, were those who came before Islam and believed in Allah without ascribing partners to Him…like Mary, Moses, Aaron etc. (peace be upon them all).
Once the Prophet (sas) came, it became mandatory on everyone who finds out about Islam, regardless of what religion he followed, to believe in Muhammad (sas) as the final messenger and accept Islam as his way of life. Failure to do so would result in disbelief.
The explanation of the ayaahs of the Quran can often be found in the Quran itself. And the ayaah that you posted is explained by this verse in Surah Baiyyinah:
**Lo! those who disbelieve, among the People of the Scripture and the idolaters, will abide in fire of hell. They are the worst of created beings. **098.006
This Ayah clearly states the final abode of those who disbelieve in any of the fundamental tenets of Islam, regardless of whether they call themselves Muslims, Jews, Christians of Buddhists.
The time one has to spend in the grave IS the akhirah. It IS the Hereafter as we know Munkar and Nakir, who will come right after a person has been burried and covered with dust, and ask the three questions. He who answers the questions will rest in peace and he who doesn’t will face the severe torture there onwards. And we know from authentic Ahadith, that only the believers will be able to answer those three questions.
Hence time spent in the grave i.e. the barzakh is part of the Hereafter.
Here are the ayaahs from Surah Tawbah stating clearly what we should do and what we shouldn’t.
Ask forgiveness for them or do not ask forgiveness for them; even if you ask forgiveness for them seventy times, Allah will not forgive them; this is because they disbelieve in Allah and His Messenger, and Allah does not guide the transgressing people. 009.080
And never offer prayer for any one of them who dies and do not stand by his grave; surely they disbelieve in Allah and His Messenger and they shall die in transgression. 009.084
well said:D