Do folks really sell their gliders so that they can pay deposit on a glider which was not built yet, knowing how common big delays are even with the most established factories? Why would anyone do that? If you really must sell your glider to buy another, buy a used glider. So many great used gliders in like new conditions out there which you can buy instantly. If you really want a brand new glider you never seen before, than you should be able to afford the financial risk and be able to keep your glider meanwhile. Otherwise it does not make sense neither financially nor flying wise.
Personally I think the GP15 sounds great, I will wait until they fly around for few years and are available for resale.

Ramy