There’s more to the story. Unless things have changed since 2013. There is a roadmap, but it’s flexible.
Disclosure Information not guaranteed, this is from an informal “chat” with a LEGO store manager 6 years ago.
There are are two streams “originals” and licensed.
Licensed sets are set by contract to a certain agreed run/qty, if the set sells better than expected then they usually (but not always) agree another run with the licensor. If a popular set does not have a new run agreed, then there’s the money for investors, assuming they bought in on that set. The Ferrari F40 (10248) comes to mind.
The VW T1 is likely under a never ending license. VW really need good publicity, they’ll take whatever they can get! Probably the bug too - why did I buy so many?
Original sets are an absolute wild car, there’s no limit other than what the market will bare, **likely** when sales drop below a certain number of units per month, per week or whatever formula is at play, that set gets scheduled for retirement. Then places, such as this, spread the rumor and we all go shopping... now sales have picked up again! Guess what production continues... Tower Bridge Tower Bridge Tower...
There are more variables at play than this