If I had to hazard a guess as to what style a new Savatage album would sound like, I would imagine that it would most likely be in the style of the last three Savatage albums (Dead Winter Dead, The Wake of Magellan, Poets and Madmen). Very rock opera and very TSO-esque, but a bit heavier. For one thing, the band for this album will most likely comprise of the DWD/TWOM line-up. For another, Europe is Savatage's biggest market, and that DWD/TWOM era of the band was their most successful over there. I would expect Jon and Zak to split lead vocals 50/50, just like what was supposed to happen for P&M. However, I would expect the album to be a bit more varied then P&M, as I would think the band would want to showcase all the sides of Savatage, and not just the darker, heavier side.
Beyond that, I don't know what else to expect. I'm not sure if it would be a rock opera or not. On the one hand, I could see Jon and the band just wanting to make a straight forward rock album. But on the other hand, the reunion might give Paul some ideas for a story. Also, Jon has often said that Streets was his favourite Savatage record, so if he wants the band to make a masterpiece, that would be the reference point for what Jon thinks is the perfect Savatage record. Plus, as stated above, DWD and TWOM were the band's biggest albums in Europe, and both of those were rock operas. So I think there is a good chance it could be a rock opera.