Yes, well said venerable Appicchato.
As nibbana is unconditioned, how could there be any 'becoming' or 'existence', for which the term "in" could apply?
SN 12.15 ( http://www.what-buddha-taught.net/acces ... .than.html
) comes to mind.
It's much easier to speak of "in" when speaking about conventional reality, rather than ultimate reality... but there's nothing much conventional about nibbana.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine