The MG3 was made by Rheinmetall, as was some early G3s. If I had to judge just based on show interest, the 433 turned more than a few heads, and might replace the rifles in some police and armed forces units that are looking for new rifles, especially if they don't want an AR or AK platform. I've mentioned the IWI Carmel a lot, and it was designed to be an competitor/alternative to the FN SCAR and such, and based on a Small Arms Review article, the 433 had a similar genesis prior to being pitched to the German Army. I can see the 433 filling that same niche.
Just like how the Carmel is the answer to the Galil Ace or Tavor not checking everyone's boxes, the 433 can fill that niche for the 416 or even the SCAR maybe.
However, not counting a photo shoot late last year for HK's 70th anniversary/board meeting and the Concamo/UFPro shoot, the 433 hasn't been seen since IWA/Enforce Tac in spring of last year. I'm not sure what to make of that. Only thing that HK has said is that they will market the 433 (and 416) to prospective buyers.