For short term visas, none of us can guarantee what will happen in the next 5 years or next 10 years.
If no more extension is allowed after 5 years or 10 years, those who own the properties there will no longer be entitled to stay long in Thailand. Unless they're willing to do a border run every few months.
The best thing about PR is, we don't have to worry for the rest of our lives staying there, though the chances of getting this visa is low.