What is the translation for 以后还得了?
不 = not
得 = able to
了 = end --&gt; be contained

不得了 (can't be contained): desperately serious; disastrous; extremely; exceedingly

Example:
乱堆的木材一着火就不得了 = Once the messily piled up timber caught fire, it (can't be contained) will be disastrous
他的快球这么强，再学会曲线球 就不得了 = His fastball is so strong if he learned curveball he will be (can't be contained) unstoppable

以后还得了? (in the future, how can he still be contained?) is a rhetorical question. It actually means 以后会不得了 (he can't be contained in the future). In other words, 'he will be extremely (outstanding/ extraordinary/ unstoppable) in the future'


Rhetorical question: &quot;How can he still be stoppable (containable) in the future?&quot;


Actual statement: &quot;He will be unstoppable (uncontainable) in the future&quot;

I would translate '以后还得了?' as &quot;How extraordinary will he be in the future?&quot;.  Meaning:  &quot;he will be great in the future&quot;