The move to the 8pm-10pm ET timeslot will now become permanent for TNA Impact. Dixie Carter made the announcement earlier today on Twitter, "Mon Night iMPACT! moves to 8 pm ET start time on Spike each Monday w/an encore performance Thursdays at 9 pm ET. Spread the word!"

Spike TV also confirmed the move.
Beginning Monday, April 12, “TNA iMPACT!” on SPIKE TV will have a new weekly timeslot on Monday nights and a new weekly encore presentation on Thursdays.

New Episodes:
Mondays: 8:00-10:00pm ET/PT

Encore Presentations:
Thursdays: 9:00-11:00pm ET/PT