Blockchain will be used not only in gambling and a payment gateway, but also it will be used on every branch of life. We have to wait to see what happen finally.
Well, the OP was not asking about blockchain uses but he was asking if blockchain could the only best option gambling gaming industries which I will say yes because in the situation where trust is needed while cheat is totally not acceptable it will get if blockchain was used.
Right now, I admitted that blockchain still the best option for gambling gaming industries but if in the future, there is a new technology besides of blockchain and that technology offers the better technology than blockchain then the position will be change. Or maybe there will be a new technology which will be used for gambling industries but still have relation with the blockchain itself.
At present blockchain is making a big change everywhere with its efficient functioning over the traditional system. Gambling industry at present hasn't adopted the blockchain technology completely, because very few gambling websites have begun to make the the entire function on the blockchain platform. Some top blockchain platforms have come forward to start their own gaming and gambling access through blockchain.