I'm actually not that worried about them secretly doing something malicious (although that's also a valid concern) but rather in the "given enough eyeballs, all bugs are shallow" and the general risk factors (MikroTik going bankrupt and we're left with obsolete bug-ridden hardware).
Sadly given the large amount of software that's closed source there I don't see them working towards open sourcing any of it as, even technically, it would be a massive effort.
Agreed, even if it was not their intent it being closed source is malicious itself - we need to promote this discourse in public conciousness so people are less afraid to question the unaudited, outsourced binary blobs that fill their day to day lives.
Sadly given the large amount of software that's closed source there I don't see them working towards open sourcing any of it as, even technically, it would be a massive effort.