Seems more likely the next battery-related improvement will be V3 supercharging - supporting much faster charging on road trips.
And with their push to profitability, also more likely Tesla will focus on reducing the costs for the current battery pack capacities, than introducing an even larger, more expensive, battery pack - that may be needed only by a small percentage of their customers.
For towing applications, it would be helpful to have a larger battery pack. Though even with the current 100 battery pack, if you select a reasonably aerodynamic trailer, you should be able to drive about 3 hours (at 55 MPH) between supercharging stops, on the order of what you get without towing (driving at full highway speeds).