Bear in mind that 20xx would not be the date prediction for the end but merely the maximum projected deadline for the end. They could play up this technicality to emphasize that they're not making a prediction of when the end is coming but merely pointing out the finite lifespan of "this generation" and that the end can come well before that date.
That way they can create the effect of a date prediction while at the same time not making an actual date prediction and emphasizing the point that they aren't making a date prediction. That way, the dubs will be more inclined to accept the non-prediction without Matthew 24:36 causing them any cognitive dissonance.