Nintendo must be so tired of Switch Mini rumors by now. The question once again came up during their most recent shareholders meeting. Surprisingly enough, Nintendo offered up their most verbose statement on the matter yet.
"We acknowledge that there have been reports [about this]. Answering to rumors and speculations would end up stealing surprises from our customers and also be unprofitable to all of our shareholders, so we have no answer to that. As a general theory, we are always performing development of new hardware."
As most will note, it's not a flat-out denial. I think that in and of itself speaks volumes.