I think the ti is the largest possible chip. If AMD was competitive, ti would have launched at the same time as the 1080 and 1070
Nah they do have the GP100 which is bigger, though the extra space isn't used for CUDA cores, but I would imagine that it could be used for more CUDAs if they wanted to. It was probably too big for a consumer product by Nvidia's profit standards and was not designed for consumers anyway.
Which is why, imo, at this point in time and if vega FE is a real indication of RX vegas performance, Nvidia would be crazy not to refresh Pascal on 12nm and tweak their GP100 for the consumer market. That would make the GP100 around 458mm² (smaller than the current GP102), and they could sell a 1080ti at around 1080 price (probably with a little premium), a 1080 at around 1070 price and so on