The topic says it all. Currently aliens gain "nothing" with their 4th hive. They can't chose a 4th upgrade. So i say lets give them the option for a 4th upgrade. If the aliens have already 4 hives it is already over anyway in 95% of all cases. This would make it easier for the aliens to end those long stalemates.
Edit: And obviously a 5th upgrade if aliens have 5 hives.
It could be a extra upgrade for the hive, like evolving it to a crag or shift hive.