All "ifs" at this point.....If Indian develops a comprehensive dealer network coast-to-coast, if their MC sales approach strong #2 status as compared to HD, if millennials and the following generations begin to buy more MC's than they do now, if Indian develops a brand loyalty that generates repeat purchasers, and if the brand stays in business, it will change the way HD does business. HD will have to downsize & close plant(s) to remain in business unless they extend their product line beyond the present offerings since they will no longer enjoy the market share they do now. Doubtful but possible.
Long term could be healthy for the MC business. Currently HD is the 800# gorilla in the cruiser zoo of weaker selling also rans/wanna bes. That can change, and if it does, bike buyers will have more choices and more competition than they do now. For the first 50 or so years of their history, HD & Indian were industry leaders. Not a bad thing if that occurs again, but a lot of HD workers will very likely no longer be employed as an end result.