Claim of Kernel sentences was dropped in 1965.
Later Chomsky dropped the claim that deep structure determined meaning.
There is nothing deep or profound about ``deep structure''. Nor do deep structures have psychological priority over surface structures. To avoid misunderstanding they were later called d-structure and s-structure.
Later theories de-emphasised transformations or dropped them completely. (The relation between competence and performance must be more abstract.)
The more complex the theory, the harder it is to explain how a child can learn such a complex system of rules. Chomsky's response has been to attempt increasingly more abstract levels of explanation. A ``Universal Grammar'', genetically determined, is converted through experience to yield ``particular grammars.'' It is not rules that are acquired, but ``principles.'' Autonomy of syntax continues.
The Principles and Parameters Framework: A general theory of syntax containing a set of (presumably two-valued) parameters which are set according to the particular language being learnt. (eg. English has SVO, Japanaese and Hindi have SOV)
One result of increasing abstraction has been the increasing importance given to the lexicon in linguistic theory. While the general features are coded in abstract rules, the lexicon contains the idiosyncratic, unpredictable features (``a list of exceptions'', Chomsky, 1995; cited in Smith, 1999, pp. 50-52).
Chomsky's later view is that the lexicon might be the locus of all variation between languages so that apart from differences in the lexicon, ``there is only one human language.'' (Chomsky 1995/ Smith 1999)
In the latest Chomskian program, called Minimalism, the d-structure and s-structures have been abolished, phrase structures have over time been eliminated. Only two levels of representation remain: the Phonetic Form (PF) and the Logical Form (LF).
(Gardner, MNS pp. 210-222 describes the evolution of Chomsky up till the early '80s.)