Hello @gschelotto,
Those dates are the ones we guarantee you we are producing them. Nevertheless, that does not mean that we are not going to produce more afterwards.
As per the recommendation if you want to change for other microcontroller with a far obsolescence, and in the same LPC1700 family, you could take a look to the LPC1788, LPC1785, LPC1778, LPC1777, LPC1776 and LPC1774, which have an obsolescence date of Oct 2028. Nonetheless, the recommendation is to take a look to what characteristics you need or want, and search something specific to you, for that please take a look to: Product Selector | NXP Semiconductors, and Product Longevity | NXP Semiconductors.
Best regards, Raul.