Truly, I say to you, there are some standing here who will not taste death until they see the Son of Man coming in his kingdom.
I’m not Christian and I’m not Jesus but many will be living the day I die.
The term till (until) after checking out the Greek definition has me understanding this passage a little differently.
Strong's Concordance
whatsoever, wheresoever, whosoever.
A primary particle, denoting a supposition, wish, possibility or uncertainty -- (what-, where-, wither-, who-)soever. Usually unexpressed except by the subjunctive or potential mood. Also contracted for
ean.
see GREEK
ean
Thayer's Greek Lexicon
STRONGS NT 302: ἄν (1)
ἄν (1), a particle indicating that something can or could occur on certain conditions, or by the combination of certain fortuitous causes.
I'm understanding this as implying an acknowledgement of knowing not being uncertain. It's an assurance of mind that the son of man is to come, the knowing and/or understanding this before tasting death or before reaching the end of their life.