Exegesis:

amēn legō humin ‘truly I say to you,’ cf. on 3.8 and 4.24.

ou mē parelthē hē genea hautē heōs an panta genētai ‘this generation shall not pass away till all things have happened,’ implying that the present generation will live to see all things happen. For the strong negation ou me cf. on 1.15. panta refers to all that has been announced in the preceding verses.

(V. 33) ho ouranos kai hē gē pareleusontai ‘heaven and earth shall pass away,’ cf. on 16.17.

hoi de logoi mou ou mē pareleusontai ‘but my words shall not pass away.’ hoi logoi mou refers to Jesus’ words in vv. 6-28. parerchomai means here ‘to lose force,’ ‘to become invalid.’

Translation:

For truly, I say to you see on 4.24; for this generation, or, ‘people of (or, living in) this generation’ see on 7.31.

Pass away. A term that fits both here and in the two occurrences in v. 33 is stylistically preferable, of course, and apparently can often be found; if not, one will have to differentiate according to meaning, e.g. ‘die’ – ‘come-to-an-end’ (twice) (Kituba), ‘be-lost’ – ‘not be-present’ (twice) (Ekari), ‘die – end – become invalid,’ and cf. ‘their (life)time comes to an end … Heaven shall end, earth shall end, but my word shall remain unchanged’ (Tzeltal). See also on 16.17.

Not … till …, if rendered literally, may imply a condition. In such a case one can better use, ‘not … before…’ (Balinese), or, invert the clause and shift to a positive wording, cf. e.g. “all these things will take place before the people now living have all died” (Good News Translation).

(V. 33) Heaven and earth, cf. on 10.21.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.