I mostly agree with what you have said, except that I believe that anyone who updates their older digital devices to a newer node now would be wise to choose 28 nm instead of 40 nm or of any other older node, unless constrained by suitability of the node for certain analog parts of the devices.
The 28 nm node is the last before FinFET, so its costs do not differ much from 40 nm, but such a choice would be much more future proof.
Already now the production capacity for 28 nm is greater than for any older nodes. Because more 28-nm plants are planned to be built, the difference in capacity will become even greater in the next years.
Choosing 40 nm now might force another process upgrade after not many years.
EDIT:
After writing above based only on the existing and planned production capacities, I have googled and I have found that representatives of TSMC have made public statements that no new plants for nodes older than 28 nm will be built, so everybody who upgrades must choose at least 28 nm (which was state-of-the-art 10 years ago):
https://www.anandtech.com/show/17470/tsmc-to-customers-time-...
While this statement is from TSMC, it is quite certain that also none of the other foundries will build new plants for nodes older than 28 nm, because they would not be able to recover their investments.