Hi,
MPC5744P will not be discontinued soon. It is included in 15-year longevity program. Its launch date is November 2014, it means MPC5744P will be manufactured at least until 2029.
See following:
http://www.nxp.com/about/about-nxp/technology-leadership/product-longevity:PRDCT_LONGEVITY_HM?&fsrch...
How you correctly said S32 is generic part number convention covering multiple platforms.
As example, I would mention new S32R having lot of common with MPC5775K
http://www.nxp.com/products/automotive-products/microcontrollers-and-processors/32-bit-power-archite...
Unfortunately, we cannot provide information about future products as they are confidential proprietary.