I own a DOCSIS 2 modem @ 10 Mb/s.
I had a casual DOCSUIS 3 modem pre-purchase concern, and a Rogers rep immediately agreed I could try a provisioned rental DOCSIS 3 modem for up to a month, and make my own measurements.
Afterwards I could make an informed choice about a DOCSIS 3 modem and/or service purchase. If I didn't want to permanently change anything, then simply return the modem and re-provision my personal one.
I haven't yet done this as I'm currently satisfied with my 10 MB/s, but this seems a very reasonable low-risk approach.