Actually I'm pretty sure I've read one interview where 242 BC. seemed to be confirmed, with ending dates still being discussed between 0 or even around 50 AD or so. I'll try to find the interview for confirmation.
242 BC seems fine with me, hopefully carthage still has western Sicily, Sardinia and Corsica under control, the Parthia and Bactria can allready be seen as separate countries making the seleucid empire less imposingly huge to start with. The only downside is that Epeiros will probably only be a minor faction in this scenario.
Edit:
Here it is:
http://www.gamersglobal.de/angetestet/rome-2?page=0,1
And because I know how scary it is for native English speakers to try figuring out a different language, here is the relevant section from google translate: ;-)
Rome 2 is about the time of the Punic Wars of the Roman Republic (from 242 BC.) Until about the year 50 AD. to cover, as the young Empire had greatly expanded the boundaries. Maybe the game is also up to the largest expansion of the Empire under Emperor Trajan (117 AD that would be). But these around 300 or even 400 years time, are translated into rounds, we did not tell James Russell. Who is not so firm in the Total War History: In Rome corresponded to each round a year ago, but changed each round as a summer and winter "season" in order to shed more tactics in the army movements. Throughout the series parts, the simulated historical periods smaller and the trains every year more numerous: In Empire, there was a year already from two trains, Shogun 2 consists of four (and four seasons), most recently at Shogun 2: Fall of the Samurai even from 24, which first required a careful planning to avoid winter campaigns. As Creative Assembly on the one hand wants to keep the seasons must, on the other hand, a Rome-2-game should last certainly not 1200 or even 7200 rounds, we are excited to see how loud the solution.
Google translate is not perfect but 242BC seems to be the date. They are even arguing about letting the game go it to the 2e century AD! nice!