Forget Mansions, the NIV promises ROOMS!!!
John 14:2
"My Father's house has many rooms; if that were not so, would I have told you that I am going there to prepare a place for you?"

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Well, that isn't really as bad as it seems. Isaiah says they are chambers in the NKJV and KJV, Rooms in the NIV, Rooms in the NASB, etc, talking about the very same thing that Yeshua referenced in John 14. The Greek and the Hebrew have equivalent meanings. So the NIV is not really off base with John 14.
Isaiah 26:19-21 (KJV) Thy dead men shall live,
together with my dead body shall they arise.
Awake and sing, ye that dwell in dust:
for thy dew is as the dew of herbs,
and the earth shall cast out the dead.
20
Come, my people, enter thou into thy chambers,
and shut thy doors about thee:
hide thyself as it were for a little moment,
until the indignation be overpast.
21 For, behold, the Lord cometh out of his place
to punish the inhabitants of the earth for their iniquity:
the earth also shall disclose her blood,
and shall no more cover her slain.