It may be extended yes, we just don't know. Don't forget the backstop will only come into existence if May's deal is passed in parliament, and that's looking unlikely at the moment.Would think the transition period will be extended. There's no way a trade deal would be finalised by the end of 2020. But the backstop is not going to be removed or be allowed to be retracted unilaterally.
Don't know what the answer is because I don't think there is an answer and there will always be different factions who will be unhappy with any agreement.