This is a variation of the acronym TTUL (Talk To You Later). Just with an S at the end. Talk To You Later Sukka.
The S is added mostly for comedy as the TTUL means later, the S is only to add a brief name call before the conversation is over. Calling a friend a Sukka is always amusing.
Alternate meaning. Can be used to say Peace out in a psudo-negative way. See description below.
When the world has gone to hell, and all proper English has completely been forgotten, people connected to the internet use this acronym to describe the phenomena of them having to talk on the computer at a later date.
The reason this is a complete scar on all of mankind is that it's an acronym that include an abbreviation.
Remember kids, 'You' is spelled with a 'Y', not a 'U'.
When forming acronyms, please keep in mind that, they are meant for shortening speech/text. If someone has to ask you what it means, you have thus failed. It then will require more effort to explain you were trying to be fancy.
George: hey i gtg, i'll ttul.
Samantha: wtf does ttul mean?
George: don't worry about it i gtg.
Samantha: wait, what does it mean, i have to know...
George: *sigh*, omg, okay, it means talk to u later.
Samantha: Oh, i thought that was ttyl.
George: Yeah, but i'm cooler than that.
*Samantha has signed off*
George: wtf.