According to Eric Nofsinger, Chief Creative Officer, there'll be a lack of spilt screen multiplayer, but still having strong online features. Apparently the team tried to enable multiplayer play using LAN, but Nintendo wouldn't have it. The game is currently penned for a June 9th 2009 US release, published by SEGA.
High Voltage seemed disappointed with the lack of local multiplayer, but suggest it might be available in a sequel to the game - something that looks very likely. We've no word on a European release date at present but late summer looks possible.
The game was also demoed by developers at Comic Con, something you can watch here:
High expectations sit on this after its impressive showing at last year's E3, will High Voltage be able to pull it off? SEGA sure hope so.