But first must he suffer many things, and be rejected of this generation.
Verily I say unto you, This generation shall not pass away, till all be fulfilled.
"They shall see the Son of man coming in the clouds of heaven with power and great glory."-Luke 21:27
"And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other."
"geneá" [translated generation] is used 13x in Matthew. The general understanding is a reference to a specific people group. You can look up the references if you wish. A "40-year group" doesn't quite fit.
"But whereunto shall I liken this generation? It is like unto children sitting in the markets, and calling unto their fellows And saying, We have piped unto you, and ye have not danced; we have mourned unto you, and ye have not lamented."
More from Strong's: ἄν (1), a particle indicating that something can or could occur on certain conditions, or by the combination of certain fortuitous causes.
Then He spoke to them a parable: “Look at the fig tree, and all the trees. When they are already budding, you see and know for yourselves that summer is now near. So you also, when you see these things happening, know that the kingdom of God is near. Assuredly, I say to you, this generation will by no means pass away ἄν till all things take place. Heaven and earth will pass away, but My words will by no means pass away.