Wasn't the same argument made when litecoin came out. I don't think anyone is going to launch an exact copy.
You pretty much said it yourself(except that we have several exact clones already). each coin has its unique features, and is thus uniquely useful in someways, unlike fiats, the success of one doesn't exclude the success of another.
All will or currently have variations on the bitcoin idea. And we haven't even had a single major corp or government try to do a coin of their own. What happens if Google or Facebook does a coin. They've experimented with their own sort of money before but it didn't take off possibly because people inherently saw it as easily manipulated but under a guise of a crypto how fast do you think googlecoin would spread?
Governments will either do it half-heartedly to prop the fiat scam further(which will fool no one and unlikely to be taken seriously), or if they abandon fiats for cryptos, then it's already "mission accomplished" for us.
About corporations, it has to benefit them in some ways to do so, if they release an open source coin which is decentralized and they have no control, it's entirely possible Bitcoin will incorporate its best attributes and evolve, if they want to take the burden of running and supporting it....well, they are looking for troubles to be honest.
(I dislike the language though)