The V4 chemistry upgrade now means each HiSeq can produce up to 1 Tb of sequence in a 6 day run. See the specs for yourself here: http://systems.illumina.com/systems/hiseq_2500_1500/performance_specifications.ilmn
For users who have generated data with v3 reagents, and for the sake of continuity would prefer to continue to do so, please get in touch to discuss this need - v3 reagents are still available for the moment.