microcontroller slew rate
Yes, that's correct.  If you're comparing to datasheet rise time maybe it would be slightly better to use 2.6V for the calculation, as the rise times are spec'd at 10% - 90% voltage instead of the full 3.3V swing.

But it hardly matters here.  Any microcontroller should have faster edges than that.  You normally would only get in trouble with slowly rising lines, e.g. an RC delay circuit, or open-collector outputs, or if the enable input is shared with a lot of capacitance for some reason.  A microcontroller with its push-pull outputs should give a really nice signal.