I think it's a pretty conservative prediction. No industry stands still. If the TPGs try, competitors will pass them. PCGS seems particularly vulnerable since they are owned by a public company where quarterly profits and climbing up the executive ladder may become more important than maintaining standards. Maybe someone will invent a computerize grading technique that will make them obsolete [I know it's been tried but technology advances]. Maybe new and better services will appear. Maybe the services will go bankrupt from mismanagement. Maybe they will be taxed or regulated into extinction. Maybe counterfeits will become so good that the TPGs will not succeed in defending their franchise. Who knows? My bet is that things will change in unpredictable and surprising ways.
I'm told that ICG coins sell much slower; they tend to sit in the case longer. On this site, there's widespread agreement we should buy the coin, not the slab. But "out there", slabs carry a lot of weight. Love it or hate it, that's the way it is. If you feel the coin is an honest MS64, based on its own merits, consider crossing it over to NGC or PCGS.
When the coin is only a $250 coin anyway, I will have to wait to justify a cross over for the expense and that will be in the future when or if the value goes up.
