Bitcoin incentive questions

How do incentives work to keep miners validating blocks in Bitcoin once there is no more block reward? Will transaction fees be enough to keep people incentivized to run the system? And if not, what are the chances that the core developers change the standard fro a 21 million BTC hardcap to include more supply? 
I’m worried that there aren’t checks and balances in the Bitcoin system that would stop this from happening, therefore making the whole “store of value” argument eventually moot because devs could just change the hardcap.