i’ll let you know 

When someone is never gonna tell you shit! Answer is typically a no!

A way to avoid an answer!

Coworker: You coming to the party tomorrow?

Me: I’ll let you know!

i’ll let you know by I know how to speak November 5, 2017

I'll let you know

The phrase that someone uses when they're never going to tell you shit.

Friend 1: Hey, are you free this week?

Friend 2: I'll let you know.

*Never talk to each other again.*

I'll let you know by Brownie72 December 26, 2011

if anything changes I'll let you know 

something you say after a lame excuse to cancel plans with friends, usually for a better offer, without any real intention of considering original plan

a guy you've been dying to go out with asks you to dinner Friday night:

Sorry Rachel - I won't be able to make it to your sister's middle school graduation Friday night - will need to work late that day but if anything changes I'll let you know.

if anything changes I'll let you know by smores21 July 19, 2012