Yes, that's a big statement in the title, so let me explain.

Lots of OSTraining customers are looking into Drupal 8 and they have questions about Drupal 8's future. If they invest in the platform today, how long will that invesment last. 

This is just my personal opinion, but I think an investment in Drupal 8 will last a long, long time.

Drupal 8 took five years. It was a mammoth undertaking, and no-one in the Drupal community has the energy for a similar re-write.