I don't think Bitcoin is forever since nothing lasts forever. However, I think bitcoin has a long standing future. In my opinion it might even replace the traditional currencies as a new type of money, the electronic money.
Yeah it's not going to be forever. It was the amazing stepping stone to a new future but it just can't be the 'one currency' forever. I do agree that it'll be around a long time and we may never see a world without it but forever means millions of billions of years. Not a chance lol.