In this, Mr Bradbourn (UK, CON) is urging the transport committee to reject the proposal. Obviously, should the transport committee decide to do this, the question of the implementation date becomes moot, as it then will no longer have a legal basis. This is the main reason of uncertainty the CAA is hinting at.
In order to increase the probability of this happening (and "this" meaning avoiding the loss of the IMC, the wipeout of the N-registry - at least those not able to afford a corporate workaround, an overall decrease in aviation safety per flown hour, etc...), it is important to write to your MEP's informing them of the disingenuities spewed by the guy dressed as a dogs dinner in seat number 154 and the overall havoc the proposal would create.
As the Chairman of the Committee pointed out, the requirement for the pilots, including those of EU based third country aircraft, to have an EASA licence is contained in Regulation 216/2008. It is this Regulation which sets the date that the implementing rules for EASA licences must come into effect. Again, as the Chairman pointed out, the Parliament approved that Regulation three years ago. If the Parliament vetoed the draft implementing rules that would not remove the requirements of 216/2008 but it would remove the transitional periods that they provide. Therefore everyone would need an EASA licence on the whatever of April 2012 but there would be no process for obtaining one. What happens then?