Yes, I think that Zencash has an excellent potential. But best moment to buy was a few months ago.

What about now?

Please forgive my ignorance but what happens to the MN payout of 3.5% when the mining rewards become unprofitable that the miners stop mining ZEN?

You can do your own calculation, Secure Nodes are still profitable.
https://zen.lebre.net/

Mining difficulty increasing, I don't see miners lost their hope.
On Contrary only small portion of coins are on exchanges and this small percentage forming the price.
https://www.coinwarz.com/difficulty-charts/zencash-difficulty-chart

Take your time and investigate more about Zen, here is an article which will probably change your picture about Zen.
https://blog.zencash.com/zencash-treasury-and-voting-model-update/?utm_source=blog+post&utm_medium=social&utm_content=R%26D&utm_campaign=Dao+model+update