It'll never happen Kovalev is a tad too small for CW, so its highly unlikely he could ever go all the way up to HW.
Unlikely to ever happen. Even if Kovalev wanted to, the financial reward would be minimal based upon the risk. It's unlikely HBO will be dishing out millions like they did with RJJ as the heavyweight division is far less lucrative these days and Kovalev is yet to establish himself as a big draw.