guys i'm sure its a diesel because last time it was an electric and the time before that it was a steam engine so if lionel is following a pattern a diesel would be next the question is what kind of diesel
here are my hopes
Amtrak P30CH
Amtrak SDP40F
GP60 / GP60M
MK5000C
any TIER 4 locomotive
AC4400
SUPER 7
BQ23-7