Actually, the other gaming tables will contribute as much, if not more, than extra capacity in the poker room. Without the draw of gamb00ling downstairs, the expansion will just be filled with more regulars.
Same thing happened in CA. When I lived out in LA and poker first happened - it was just poker (lowball draw actually) and the places became inundated with regs. Same thing, most were not good players, but better than the average tourist-type that staggers in from the pit. When they introduced BJ and Asian games, the rooms became a sea of human ATM's. Of course, that mellowed as more people became regs and got (slightly) more proficient. But, to this day some of the best rooms *anywhere* are: Commerce in SoCal and Bay101 in NorCal.
With some luck, we may just experience a little of that phenomenon at Parx