There are only 15 more GeN4 Pre-Order licenses available. After these are done, the shop will be closed and you will have to pay the full price for Gen4.
Currently you can purchase GeN3 and the GeN4 pre-order for $127 using the coupon GeN4Promotion. After all these licenses are bought, GeN4 will cost $200 for the lifetime license.
Hurry up if you want it cheap!