Skywarp is as dumb as a bag of hammers. He lacks common sense and creativity, and needs to be constantly supervised and told what to do to make him effective on the battlefield. He's a mere follower, not a leader. If he was leadership material, he would've been cunning enough to use his teleportation powers more effectively.
I think Onslaught has what it takes to be replacement Decepticon leader since he's very tactical and strategic.

Skywarp
Soundwave wasn't decisive enough. Shockwave in the tv show was more a steward of Cybertron than a leadership candidate.(his comic book persona was awesome).
Starscream was an idiot who failed leading the Combaticons. Skywarp seemed to share at least some of Megatron's vision & perspectives.
my essential 50
http://www.imdb.com/list/ls056413299/

Shockwave would've been the best replacement, he could've used the space bridge and came to Earth to take over for Megatron.

Soundwave would have been more successful. He is the smartest transformer by far. He's cold, emotionless and a mastermind strategist.
Starscream would have led the Decepticons to disaster, he's way too emotional.

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