There is nothing preventing it from a technical perspective. The system uses a 3.5 day median of the price feeds for all calculations, so if a group of witnesses decided to try and do something that was not in the best interest of the stakeholders/network, then the stakeholders would be able to vote them out.

FYI, STEEM is not limited like BTC. The inflation rate will continue to go down over the next ~19-20 years, but it will never reach zero. (More details are in the bluepaper/whitepaper.)