When people get new bitcoins that aren't spendable in certain locations, it will be interesting to say the least. Then the government will force everyone to "accept all bitcoins".
There will be some groundwork done. Powerful people will be coopted. Developers, mining pool operators, exchange operators, merchants, whales etc. Propaganda will be used to convince ordinary users of the need for change. Then there will be a fork and whichever chain gets the majority's support will become defacto bitcoin. Those who persist with the old chain will have their wealth instantly wiped out.
Governments have a history of taking over private property. The Romans used to do it to every noble family that crossed the emperor. They even stole from soldiers who were away fighting for the empire!
The overwhelming super majority loses in the "inflat-a-coin" fork, the only ones who would benefit would be miners and even that is debatable. The fork and the resulting confusion would have a cost. Miners unlike coinholders also face a real risk, they can't mine both chains and their mining rewards would only exist on one side of the fork. If the choose wrong they run the risk of ending up with worthless coins.
Also we aren't just talking about slack jawed idiots here. If Bitcoin survives and grows the "Bitcoin wealthy" would include major corporations, millionaires, billionaires, sovereign wealth funds, hedge funds, ETFs, family wealth funds, etc and they ALL would have their wealth devalued by raising the cap. It is a pretty easy and transparent choice.
If it happens then Bitcoin is dead anyways. Still it is pretty easy to hedge your bets. Sell off your inflat-a-coins, keep your bitcoin and buy assets this the procedes. If you guess wrong and the old fork dies you can always buy the new coins back with the proceeds.