Saying "Out of the top 10 fatal health problems, at least one will become easy to cure in the medium-term future." is quite fair given this trend. "This particular currently fatal problem will become easy to cure.", much less so.
Right, which gives us "This particular currently fatal problem has at least a one in ten chance of becoming easy to cure" unless we have some reason to think it won't be the one.
Luke Parrish points me to what is clearly by far the most serious critique of cryonics ever written: a 57-page treatment by Evelina Martinenaite and Juliette Tavenier, presented as a 3rd semester project at Roskilde University in Denmark supervised by Ole Andersen.
Full paper