Northfoto / Shutterstock.com Suspense is dead because Twitter killed it. Surprisingly, R.E.M. bassist Mike Mills overheard that Late Show host David Letterman will be announcing his retirement in 2015 Thursday evening. Dave just announced his retirement #2015 #muchlovedave— Mike Mills (@m_millsey) April 3, 2014 David Letterman announces he's retiring next year. More tonight @CBSEveningNews— Jeff […]