What happens next depends on whether bitcoin's rivals can gain usage for their coins.
With all these ICOs going and popping around, there's like a whole lot of usage for the coins.
The usage for most of the new coins from the recent ICOs is not even huge yet except for few of them. Over time, when we start seeing real life usage for most of them with a product especially, then we will start seeing some great development for them.
All the above, I would not call them a rival for bitcoin as bitcoin has been able to set a huge pace and being able to catch up is not something I see for any of these alts.