Some companies wait a couple of months before releasing a trial because they know the first commercial version released to the public is going to have a ton of bugs not caught by their internal QA.
They don’t want to scare away potential customers with a hella buggy demo. (They wait for their paying customers to report those bugs first!).
Steinberg has followed this pattern before (making demos available a few months after release), so I expect there will be a demo sometime after the first major service pack is released for Cubase 8. I noticed they don’t have a Cubase 8 “elements” version out yet either. I wonder if they’ll do one of those too?