It's not going to happen any time soon ... if at all. Assuming the current reunion releases a new album, does a world tour and then call it quits you're looking at 2014 (and that presumes they don't continue for further albums/tours). Then there are other projects which would probably come first like Tony's film scores, and the side project with Ian Gillan so we could be looking another year or two after that.
Only use the name Heaven and Hell as a marker for any future project as it's highly unlikely they would use that name out of respect for Ronnies legacy, if it was Martin era stuff (and assuming that the Tony's settled their differences) it would probably have some name relating to a Martin era album. It's been suggested on these boards that Headless Cross would be a suitable name. Personally I don't think any of the Martin era album titles lend themselves to a band name (I didn't much like the name Heaven And Hell come to that), so a track name like Black Moon or Heaven in Black etc. would be my choice.
As for whether Tony Martin would suit the project ... yeah why not, he's a really good singer who's done it before, doesn't want to work with Iommi though as far as I can gather. More a question of would Vinnie want to do non-Ozzy/Dio material?