Hi
I would be really nice to have DNS and rDNS server implemented in the RouterOS.
DNS - I mean full featured DNS where you can manage your own zones.

+1
Not a bad idea actually.

I think the RouterOS interface would be really well suited to this, of course it would need some kind of Primary/Slave setting as well so you could have a nice matching pair as authoritative nameservers for domains.

It depends. If they would take some existing software, added nice GUI (standard RouterOS-like) and made it into optional package, then great, dream come true. But MikroTik likes to make some things from scratch, and if that should happen, then with heavy heart, rather not. DNS server seems simple, but it's not what it used to be. Full-featured server is lot of work. And rather than another OpenVPN (read half of features missing and users begging for them for years), it's better to not get anyone's hopes up. Few tiny improvents to existing DNS cache are different matter.