Given that we don't have any evidence of cryonics working (as far as I know, no successful revival has been ever done), it is only hoped that it might work some day in the future.

Successful revival doesn't seem it's the right thing to look at--but there are probably preservation metrics that we can track and judge cryonics organizations by, like time involved in suspension, some metrics of how well the suspension went, and so on. One might be also interested if anything happened in the wake of Melody Maxim's criticisms 5 years ago (I haven't looked into it since then).