If you notice, some retailers (USA retailers in particular) have started listing releases by quarter (like, "first quarter 2007"). This will be more reliable, but still subject to some slippage. This is the main reason I have stopped pre-ordering Corgi. Of course, the new management took the absense of pre-orders as cause to fully CANCEL some of the models I fully intended to purchase.
Hopefully, their schedule will improve with the new management. But, it should be noted that almost no other manufacturer publishes their release schedule so far in advance. Indeed, Gemini Jets and AeroClassics only announce releases when the boat leaves China (literally)! Dragon generally gives us about 1 to 2 months notice, but even then, their releases invariably slip one or two months further. Admiral and Hobby Master sometimes give us a heads-up, but rarely set a date certain for availability.