Well, that's the hottest issue of the last few years. It's miners who are the ones who can activate it.
Some miners can't be bothered to signal for any change. Some miners are signalling for Segwit. Others are actively trying to block it.
Some say that's because Segwit would remove an advantage they have to save power and increase profitability. Others think it's because they don't want a centralised development team to lord over Bitcoin forever. Others think it's a pure power grab so they can turn it into something even more centralised.
One thing I am sure of is that it's getting old.