Ok, first of all, there are a lot of sources on the internet that are merely rumours. If you want true clarification or information about Rome: Total War being available for the Mac, visit the authentic webpage designed by the developers, Creative Assembly.
http://www.totalwar.com. Only there can you get the official details. Don't even listen to other sites.
Secondly, there's been no evidence at all to suggest Empire: Total War will be introduced to the Mac. The publishers of Empire: Total War, SEGA, have mentioned nothing whatsoever and their "search for a game" database clearly displays "PC" only.
http://www.sega-australia.com/games/?g=2…
Thirdly and finally, if we assume Rome: Total War is coming out for the Mac (which I doubt it is), it's taken 7 years to do so. In comparison, you might be waiting until 2016 for Empire: Total War to be released on the Mac.
Gamer.