A long and complicated story behind it, but no, VM can't just increase their upload speeds - the core cable technology permits around 10:1 ratios. Within that there's some leeway to offer more to some customers than others, but overall the ratio holds true.
As and when VM have a true fibre offer that's not got a DOCSIS element in the chain then yes they can consider symmetrical speeds (which is not to say that the economics will make that attractive to VM), but for this even to be an option they'll need to have upgraded the network to XGS-PON, and the customer droplinks, as well as replacing the customer's hub. That's part of the strategy but it is years away. If you want faster upload, go with CityFibre. If you want VM's bundles, TV offering, regular massive price rises, and top notch customer service then stick with VM.