No they didn't.
The agreement was entirely around those currently in the UK (up to March next year).
It did not cover the movement of people after that, as that would (of necessity) be tied to the nature of the transitional agreement.
You can read it here (though it's deadly dull). Quoting para 6:
"
The overall objective of the Withdrawal Agreement with respect to citizens' rights is
to provide reciprocal protection for Union and UK citizens, to enable the effective
exercise of rights derived from Union law and based on past life choices, where
those citizens have exercised free movement rights by the specified date.
"
It does not cover those moving post-withdrawal.
"This does not prejudge any adaptations that might be appropriate in case transitional arrangements were to be agreed in the second phase of the negotiations ..."
It looks to me (and the EU, by their reaction) that May has defined two different "specified dates", one being March 2019 and the other being the end of the transitional period. Cake and eat it, in other words.

