13 Pro: 203g
13 Pro Max: 238g
So the Pro Max is 1.17x the weight of the Pro. If the 14 weighs about the same as the 13 (173g) and the above holds true, you might expect the 14 Max to be approximately 203g. Take that with a big pinch of salt though, there's no guarantee the 14 won't be heavier than the 13 in the first place, or that the ratio will be similar for the non pro phones, but that's about as good as you're going to get for a guess in the absence of any rumours.