Fully featured DNS server would be too much work for too small target audience, so there's no chance to get it in ROS, I guess. Unless MikroTik decided to include e.g. BIND, but I don't think so. Not that I would protest against optional package with this functionality.
But they could at least add these simple features:
1) Allow to add more types of static records. Now they allow A records, so the required ground for adding more is there. It's simply a matter of adding user interface for few other common types.
2) Add support for per-domain forwarding to external resolvers, so user could say that e.g. everything under company.local should be forwarded to resolver 192.168.1.10, instead of to default resolvers configured under /ip dns.
Neither requires any big changes, the basic framework is there already. And once it's done, it doesn't need to be touched again for years. It's so simple there's not even any place for bugs.