This sorta came up elsewhere so I thought I'd move the discussion about the rules to the proper place.
Under the standard rules can you premeasure a decloak action the same way you do a barrel roll or boost?
I'm inclined to say no, for the following reasons.
In the standard rules on page 8 it mentions that you can measure before committing to this action.
In the FAQ it says the same thing about Boosts on page 17 as part of the FAQ section. It does not mention decloaking here. However in the FAQ section under movement and actions and game effects it mentions decloak, barrel roll or boost in regards to moving off the table.
So they updated those two sections to include Decloaking.
Finally if you look at "Echo" in the FAQ it says
If “Echo” can perform the decloak, she must do so.
This being the same wording for the competitive rules for barrel roll and boost. This part of the FAQ should apply to both Standard and Competitive rule sets.
So unless I've missed something, once you declare your intention to decloak, you're stuck having to do it, if able to. You can't premeasure, and are committed to the action under both the standard and competitive rules.