Yes, it is dependent on the date of activation but I’d still be careful. The box might contain an activation code for WaveLab 8.0 only, and if activated after the start of the grace period for WaveLab 8.5 (i.e. today) then the user would be entitled to a grace-period free update to WaveLab 8.5, but possibly not to WaveLab 9.0.
The best thing would be to clarify from Thomann exactly what’s in the box, then raise a support ticket with Steinberg to clarify the position with regard to the grace period and whether you’d be entitled to a grace period update to 9.0.