When in hole, stop digging?

So now it appears that Brexit no longer means Brexit, but Brexit deferred?  And deferred by how long?  The Prime Minister in her recent speech was carefully vague.  She talked of a "double lock" giving people the certainty that the period will be "time limited" and "will not go on for ever", but when it came to specifics, was prepared to do no more than suggest "about two years".  Which takes us to at least 2021. and who knows what the situation will be - and indeed who will be in power - by then.  Plenty of wiggle-room!