Honestly, if I were the Disney execs making this decision, I would not allow no-expiration options at all. To have the expectation that you can buy a 10-day ticket, and take 2 5 day trips is absurd. I don't mean this as a flame (just my humble opinion), but I haven't seen a single reason that adequately demonstrates the position that this is something that Disney is required/should be offering; All I've seen are people being angry that they'll have to pay more now.
It's like going to a store, and buying a 12 pack of hamburger buns, and expecting to be able to use 6 now, and then come back in a year and grab the other 6. Discounts are offered for bulk purchases in the immediacy - not to use some time later. I mean, I get that we as consumers don't want to pay more for a product we already get for less, but frankly, this should be more of a "darn - it was great while it lasted" rather than a "woe is us! Disney's screwing us!"
All that said, I do blame Disney for ever offering this option; from a business perspective - terrible idea.
People buy 12 hamburger buns, use 6 now and freeze 6 for later use. OK maybe not buns but certainly meat.
Years ago virtually all Disney tickets never expired. There was a discount, but not a huge discount, as you added days. MYW tikcets allowed guests to add extra days for literally a few dollars. The intent was those days would be used during your current trip. The extra cost to add non-expiry went up at least once. Basically to remove the significant discount you received in adding extra days to a base ticket.
Disney could just increase the cost for no-expiry. Make it even less attractive.
Add me to the posters who think the RFID wrist bands may be the reason why Disney might wind up getting rid of no-expiry altogether.