I like these changes.. am waiting for years to get scalar type hints.
They will save a lot of sanitizing code.
The newer WB code will have only less problems to be adapted.
Right now we already use "good will" type hints. See the notation for variables from WB2.8.4 (i.e. $sString, $iInteger, $fFloat, $aArray, $oObject a.s.o.). SPL-types has been unliked crutches only.
All other incompatibilities will not make too much trouble... i hope..
How it looks at modules? It's better don't think about.