At what point do old customers get the new routers ?

Simple answer rarely. You are provided with a hub suitable for the speed of your plan. If it fails it will be replaced free of charge, usually with the same model, often a refurbished one, but in rare cases you may get an upgrade hub. You cannot just request a new hub.

The standard is 1Gb port which 1Gb going over should get a hub 5 with 2.5Gb port but 1Gb in VM eyes is 1Gb port is fine for 1Gb package.

I would like a hub 5 too even if I stay on old Docsis to the last dyeing days that if I get a hub 3 to the point that ends that a hub5 would have been a better option to go with in the first place right up to they change me to fibre and if I get a modem mode option.

VM don't care about wifi if you want better get your own router 1Gb port is what VM go by so if you don't like the hub use modem mode with your own router.

Also VM can't just upgrade everyone thats a lot of hubs that need to be made people way back on old stuff who will likely stay with VM with old hubs need upgrading first.