Ya never know, you might see one more update for the Plus and 520 but if we use history as a guide the one assurance is that a new problem would be introduced. We can see similar histories with DJI, Apple, Microsoft, Firefox, and other brands.
If the current firmware is stable and provides what you needed when you first bought the product further updates are unnecessary. If the product will not do what was needed when you bought it the problem is not due to a lack of firmware updates, but a failure to fully research a product before purchase.
Not to beat a horse but this is where we fail ourselves. Manufacturers have no incentive to deliver products that function perfectly out of the box when their customers buy them knowing they will have defects or deficiencies in hardware or firmware, hoping later firmware updates will correct them. We should also remember that firmware cannot fully correct hardware problems. Firmware can help mitigate a hardware problem but something will always be sacrificed in mitigation.
Manufacturers DO have incentive to provide fully tested and functionally correct products when people WILL NOT buy deficient or defective products. So determine what you need or want, do your research, buy what fits the need, test everything in the first two days after purchase. If it all works correctly, be happy. It it doesn’t, return it for a refund on the third day and buy something else. I say three days because most states have a recission period that allows a buyer to return a product for a full refund. Yuneec also has that policy.