Here is my idea
For all the states that are gaining congressional seats, the new seat has to have the most population growth possible the past 10 years. For instance, in Georgia I made a new seat that takes in Forsyth, Cherokee, and eastern Gwinnett counties. The district grew about 50% from 2000.
Since it is likely that same areas will continue to grow at a high rate, this will maximize the deviation in the future. Thus it would be a deliberate effort to deny equal protection, and unconstitutional.
In Australia, reapportionment is done on a continuing basis, whenever a state is apportioned an additional seat or loses a seat. or whenever the deviation between district populations is too large. They project future growth and deliberately draw smaller districts in those areas. The idea is that population equality will be reached in a few years, and then the districts will cross over. Districts that are initially low in population will grow to have more population towards the end of the period.
So in the US, it would better to use projected 2015 populations, and use the ACS to check whether districts are getting out of line or not.