If it accepted alts but not bitcoin, I think this would be the first case, and something very negative for bitcoin, as until now, merchants were accepting bitcoin or bitcoin and alts.
I doubt this being a negative impact on Bitcoin. Cryptocurrencies have their own implementation advantages so if one is not suitable for the task then resort to another one. That's just how it is. Since Bitcoin transaction takes time to be confirmed, and transaction fees are much higher than other coins. So litecoin/ethereum should be suitable for their business.
I think it is more likely that they will issue their own crypto, as its been said.
Perhaps. However, I think they should have their own coin and not a token. If they are going for a new token, such as ERC20, then they should've used ETH instead.