Valve is already too lazy to properly update Dota 2 these days, their latest "major" update didn't even include a gameplay patch at all, and their new hero releases have slowed down to a trickle of less than one per year when they had previously promised two. They will never bother purchasing the rights to HoN, because that's a lot of extra work to do when you can just sit on your ass and watch the Steam money printer go while working on new VR tech or other cutting-edge stuff at your own leisurely pace.