After 8/4/2012, are all new licenses issued going to be EASA
No, the UK will continue to issue the NPPL for use on Annex II aircraft and, additionally, will recommence issuing the national PPL, CPL and ATPL for the same purpose.
At present, there is a conversion path from NPPL(M) to NPPL(SSEA). Will that disappear after....
No, but the licence will be valid only on Annex II SSEAs
what about the EASA LAPL?
There are currently no crediting arrangements for the NPPL towards the LAPL, although that is not say that such arrangements will not be developed before 8/4/2012.
Your JAA ATPL will not be an EASA compliant licence
All licences issued in accordance with JAR-FCL will be deemed to be EASA licences from 8/4/2012. When the current JAA ATPL expires it will be replaced with the EASA equivalent. In the UK, an EASA ATPL(A) that includes an SEP Class Rating will be valid on an Annex II SEP aeroplane