Going forward, new LPC MCUs will generally be supported in MCUXpresso IDE via the provision of an SDK. SDKs for some existing parts may also start to appear over time, but I can't make any comment at this stage as to which and when.
MCUXpresso IDE contains built in support for a slightly extended set of LPC Cortex-M based parts that were supported in LPCXpresso IDE v8.2.2. It does not however contain support for the old ARM7/ARM9 based LPC2000 and LPC3000 families.
For more information on differences between MCUXpresso IDE and LPCXpresso IDE, I would suggest looking at the MCUXpresso IDE documentation, starting with the Installation Guide. The documentation can all be accessed online via http://www.nxp.com/mcuxpresso/ide/documentation.
If you have more questions on MCUXpresso IDE, I would suggest posting them on the MCUXpresso IDE forum : https://community.nxp.com/community/mcuxpresso/mcuxpresso-ide
Regards,
MCUXpresso IDE Support