The direct debit is still a years worth of Tax, just paid for in monthly installments. There is nothing in there to suggest they are moving away from a system of paying for Tax a year at a time.
This appears to be the start of a move to push people towards paying monthly rather then annually. Once this is common practice VED will rise simply because people will be less likely to kick up a fuss over a £5 per month rise than they will a £60 per year one.
Call me a cynic but an "overhaul of vehicle excise duty." is unlikely to result in many people paying less to the government than they do now.

(It's trailered to most events but kept road legal for the occasional road test, moving it to the place the trailer is stored and as backup if one of the dailies is off the road.)