The rumours I've heard suggest that the new walker is £70 so lets hope its even bigger!
I am really torn on that price tag, on one hand it breaks the £50 mark which psycologically drives people away from it, on the other hand it brings it in line with the baneblade in price so is plausible.
To justify the £70 the kit needs to be pretty damned big, the size comparison with the tau walker suggests it is big, but not +£20 big.
If it is £70 then it is likely on the higher end of the guesses/comparisons, it is not going to be bought by everyone, and will therefore have quite a bit of wow factor in an army - not every one is going to have one.
If it is £50 it is likely going to be comparable to the tau one (a couple of inches taller), more comonplace in armies, and fielded in triplicate in my apocalypse army.