There have been such ideas before. Some people clearly want it, and I'm sure that MikroTik would like if they bought their hardware to run it, instead of some PC with Linux and whatever DNS software that does the job for them.
On the other hand, there wasn't too many of these requests, at least publicly posted in this forum. Plus IMHO it would make no sense to do half-assed job and only provide simple recursive resolver. If they should create something (as a *optional* package of course; that's for "pure router" fan club
), it should have all modern features (DNSSEC, ...). And that, combined with probably low demand, might be too much.
Perhaps using some existing software (e.g. Unbound is even BSD-licensed, so they could do pretty much anything with it) could be the way. Package it for RouterOS, add nice and friendly WinBox/WebFig/CLI interface for it... that could be a dream come true.
But the realistic answer is probably "keep dreaming".