User blog comment:NOS Sterling/Sonic Boom could bring two more fan favorite characters/@comment-24375505-20140814105208

"Gravitate towards characters that best fit into our objective to make an epic adventure game."

Judging by what we know so far, time-travel is appearing in Sonic Boom. So one of those characters will most likely, not definitely, be Silver. And we assosiate Chaos Emeralds with Shadow, so Chaos Crystals and Shadow, equals high chance of him appearing.