Since ERC20 is a protocol standard for trading, I believe the future of such tokens depends on their quality and of the product they are related to. Taking for example, AppCoins, a crypto asset for the app economy. They are aimed for an industry that forecasts to double in value and users by 2020, so projections are that it will increase its value on the next few years. As for fork coins, considering all the trouble involved on software update and all, I think they are trickier to work with.