I have copied this article written by the Admin, James Brannan, of the Remain In France Together - Citizen's Rights facebook page.
'Once Johnson gets his Withdrawal Agreement (WA) through Parliament and Brexit takes place shortly thereafter, the next phase is characterised as talks on trade, but it will actually be about the entire future UK/EU relationship covering political, cultural and security arrangements (there will be a number of “strands” of negotiation in parallel). The transition expiry was set at a time when the exit date was supposed to be 30 March 2019 so we will have lost 10 months of a 21-month transition period.
So it would be important to extend the transition (or implementation) period beyond 31/12/20 not only to finalise a trade deal but for various reasons related to citizens’ rights and the maintaining of existing EU law (especially on freedom of movement and non-discrimination) for a bit longer: (1) to give time to the EU27 States to adapt their legislation to the citizens’ rights part of the WA; (2) to allow both the EU and the UK to finalise their agreements on bilateral matters such as social security coordination or (hopefully) ongoing freedom of movement for us; (3) generally to maintain the status quo as long as possible, retaining free movement until a later cut-off date for residence rights (for example, the French CdS or driving licence wouldn’t become mandatory until a year or two later); (4) to extend in time the application of rights which will run for a certain period from the end of the transition (e.g. ECJ jurisdiction for EU nationals in UK, home rates at UK universities for British children in EU27, etc.); (5) generally to extend the deadlines to give citizens more time to complete formalities and to plan ahead.
A longer transition will have to be decided by the end of June 2020 and could be for one year or two (Article 132 of the WA). You will have heard the news this morning that Johnson will seek to rule out such an extension already in the implementing legislation that he will put back to Parliament. It is clearly unacceptable to preclude the operation of the relevant provision of the WA at this stage, especially as an extension would have to be decided by the Joint Committee and therefore it could be requested by the EU – it’s not a unilateral decision of the UK. Of course we know that Johnson is taking this position because of the promises he made during the campaign, not least to Farage, but such a provision of UK law clearly runs counter to the spirit of the agreement with the EU and the principle of sincere cooperation. After the Second Reading of the Bill we can only hope that this provision will be amended or removed to allow for the possibility of an extension and it will be worthwhile lobbying MPs on this issue.,