VZW-Sprint is fairly unlikely- it'd probably be too big even for the very loose merger regulators (we'd be talking well over 100 million customers)... plus, VZ(W) has a rather large debtload- nothing to worry about right now, but they might have issues borrowing enough money in the future.
Plus, there'd probably be antitrust issues on the wireline side, what with VZ owning the ex-MCI network.
