Widebody Order Gaps

A lot has been written in the past about the orders that Airbus and Boeing need for the A330ceo and the B777 (non-X) to fill the production lines until the A330neo and the B777X will take over full production.
I started to collect the backlogs for both aircraft every month to see how the backlog will change over time. With the current or announced future production rates I can then calculate how many orders both aircraft will need.
Of course there are some open questions that will influence the number orders needed to fill the so-called gap:

• How will production rates change until the new aircraft will enter service
• How long will it take until the new aircraft will take over full production

For the A330ceo Airbus already announced a decrease of the build rate, going from 10/month to 9/month in the fourth quarter this year.
Boeing did not yet announce any production cuts for the B777, staying at a rate of 8.3/month of 100 per year.

As I don't know how long it will take for the new aircraft to take over full production I will only calculate the numbers until EIS of the two aircraft.

Here is what I get for the A330ceo:

Airbus would need another 129 orders until EIS of the A330ceo to keep the production line output at 9 aircraft per month. Airbus already admitted that the rate has to be cut further down but has not yet indicated when and by how much.

And here is what I get for the B777:

Boeing would need another 218 orders for the B777 (-200LR, -300ER,-F) to keep the output at 8.3/month until EIS of the B777X. Boeing until today is confident that they will sell about 60 aircraft a year to fill all these slots without cutting the production rates.

To keep output steady until the two new aircraft take over full production a lot more aircraft need to be sold. I highly doubt that this will be possible. Airbus seems to be more open and honest about that.