for me. I dont think something greater than BTC will come sooner. Everything that were looking for in an alternative currency can be found in bitcoin. everything that were looking for in an alternative currency can be found in bitcoin. Now that most of online casinos and other business owners are starting to accept it, I dont think they will accept new one soon, if ever there will be.
Not soon but in the future. I think that other coins existing now cannot replace bitcoin, because all of them are created based on bitcoin. If someone created another coins but not based on bitcoin, I think that coin have the ability to replace bitcoin. As we can see, today's technology is upgrading fast, so its possible that in the future, someone might create better crypto currency than bitcoin, and it can caused bitcoin to be replaced by that coin, bitcoin might die.