On Sunday, June 28, 2020 at 12:17:49 AM UTC-4, Eric Greenwell wrote:
I know glider delivery dates, especially for new models from
any manufacturer, tend to drift into the future.

So they do.
I've waited on average some years after initial "promises".
Only once had one show up ~on time (even a bit early).
Don't sell the current glider until the new one is on the boat!
Of course, if getting a motorglider, you need a spare glider anyway...