Yes, I think you are conflating two different issues here. That God speaks to us today by a variety of means is not in question. Whether thru His word, the Holy Spirit, prayer, a sermon, the wise counsel of a Christian friend, etc. All are means that God uses to speak to us today.
The subject under discussion (as I understood it) was whether a false prophet can still be a true believer with a valid ministry? I would argue that presuming to speak on God's behalf on matters that are explicitly proscribed by Scripture (date-setting being one of them) is sufficient grounds for disqualification as a teacher. But to conclude that such a person is beyond hope or redemption is a step too far.
I doubt that Wilkerson, Wurmbandt or Lindsay (et. al) deliberately set out to deceive their 'flocks', yet to the extent they were believed, that is precisely what they did. I don't want to second-guess their motives for going down that road (I have my own theory about that), but history is littered with lives that have been wrecked by exactly this kind of hubris.
The lesson is a basic one that any professing Christian ignores at their peril - if Scripture says don't do it, then ............well, I think you can work that one out for yourself.