I also think voice chat isn't a bad idea, but I think it would likely be extremely difficult to implement. If their servers are already having trouble managing the influx of players, voice chat would likely be A LOT of extra strain. (Not to mention the specifics of the implementation, and the fact that randoms with voice chat might actually drive the quality of gameplay down if they're really prone to screaming at each other.)
Personally, I would not be at all disappointed if the devs focused on the core stuff first, and then built from there. They've obviously already got something really fun!