It may be worth having a look at the RV14 Forum and work out the development timeline from Van’s unveiling the flying prototype to the point where all of the kits were available and the manual was ready for first time builders. They took a few years getting the kits together and getting the very experienced early builders to work through the major problems[edit: that’s a bit steep! More like iron out the kinks and work on the optimal build sequence, improving the initial build manual along the way…]. I think it was roughly 2012 first reveal and 2016 (? - I’m sure someone can correct this without me doing any research
) when all of the kits were available to mortals. They drip fed the kits during that period but there were a number of first time builders who jumped in early with each kit and had a prolonged wait for the next kit to be available. If those timescales are roughly accurate it could be 2026 before you get your last kit, so maybe first flight in this decade?
Alternatively, if you work regularly on it, and the delivery times for the existing kits don’t stay so elongated, it is feasible that you could order a 10 now and be complete by the time the early adopters have done the R&D on the 15 for you. Then you can decide if the 10 is fine or start on the 15 and sell the 10 when you need to release funds for the big purchases.