Could be. 也许是. 有可能是.
It's likely. 很有可能. It's possible. 有此可能.
It's anyone's guess. 是非曲直没人敢肯定 It's merely guess upon guess. 这只是乱猜一气罢了.
I don't deal with "what if's." 我从不做没把握的事. You're either dead sure or dead. 如果你没完全的把握准死无疑.