420 new trainees with 7 years equals 60 per year, or 120 in the two year period stated. Look at normal attrition due to retirement, health etc, lets say it's 5%/2%, so that's 35 Captains and 16 First Officers per year, 102 for a two year period.
Then look at the fleet plans for the next two years. Is there a sufficient crew surplus to replace all expats?
Finally look at who made the statement.
However, it is worth mentioning that it appears that ALL expat recruitment is now stopped.
Mutt