Literally everyone I know personally from before Trump existed who is now claiming they will vote Trump have never voted republican before and most have voted democrat the majority of times in the past (and third party other times).
So while I certainly cant speak for how big of a trend it is, I can say I have seen it in droves personally.
I can even say I've been so deeply hurt by other democrats despite the fact that I voted for obama and have quite voted democrat in the past I have decided I can no longer support them moving forward given the deplorable way they treat people. While I also cant in good conscious vote Trump I can say it certainly has lost my democrat vote.