Well I don't think many would be surprised if a new route didn't use at least one existing piece of stock, I doubt you will see many new routes with two of three new items of stock, it adds to the overheads of creating a route, business do cost things! That still leaves a lot of scope and I suspect there will be one new piece of stock either a loco or multiple unit at least! If it is a modern route then it will likely be GWR or Southern as they obviously have their licences. I wouldn't rule out (and hope for) another BR period route. Looking at the stock released so far on the BR blue routes, it wouldn't have to be a northern route it could be almost anywhere in the UK, the class 101's were widespread as were the 31 and 47 and the Peaks could be seen in the North, the Midlands, North Wales and the South West.