T-Mobile has decided to pull the plug on its Sidekick 4G smartphone and is, for now, putting the Sidekick line of smartphones on hold until further notice. Our friends at The Verge reached out to the carrier and were told “While the T-Mobile Sidekick 4G is being retired, it doesn’t mean we are discontinuing the T-Mobile Sidekick line. T-Mobile continues to update and expand its 4G product portfolio and we’ll keep you posted when we have news to share on T-Mobile’s latest 4G devices.” The T-Mobile Sidekick line is best known for the slide-up or flip-out full QWERTY keyboard found on its devices.