Not sure where you live, but if it's Lower Mainland, I believe Kinetik Cycles in Coquitlam had a Sight demo program this summer.
I also made the jump from a five year old 27.5 to new modern geo 29er recently. Went from a reach of 440 to 480 and a wheelbase of 1188 to 1248. It was a big jump for me and I was worried it would be too long, but feels really nice. Definitely way more of a charger than my old bike. A few strikes though, not as nimble in the tight old school trails and not as flickable on jumps. And don't rely on a parking lot test, these new long bikes feel like tanks in the parking lot. You really need to get them onto the trails with some serious vert to see how they really feel.