You're making an assumption that the "new" blades are better in design than the old blades and that Robinson will not pull the rug out from under you with a future AD.
The new blades are better, this is not an assumption. As for getting hit with expensive ADs, this can happen to any airframe at any time. Indeed, there seems to be a number of Boeing aircraft dealing with such issues right now. Hell, there were 43 FAA ADs issued in the last 60 days alone:
https://www.faa.gov/regulations_poli...ss_directives/