I've just got an email offering a box swap for my old V +Box. The V+ box is my secondary one and the replacement TiVO will be bigger than my main one so will the engineer be able to swap them around as well.
I'd like to thank you for asking this question. We are currently only replacing certain models of the V+ box so the technician would not be able to change your newer V+ box at this moment in time. To my knowledge there are not plans at the moment to change the other V+ boxes, however who knows what the future may hold.
Should you wish, you can most certainly use your existing "Main" box as your second box, and your TiVo® as your main box, the technician will be able to move these if you don't want to move them around yourself.