Is It Too Big ? - Customer Data Warehouse Growth Projection

I have a customer using Postgresql for a data warehouse. Their current
setup is :

5G database with a 50M data load each week.

They are running Pg 7.1.3 on Redhat 7.2
the platform is a dual P1000+768M Ram+5x18G 15000 rpm scsi with raid 5

Their growth projections are :
1 month 30G database with a 300M weekly load
3 months 60G database with a 600M weekly load
4 months 300G database with a 3000M weekly load

I would appreciate any suggestions on how to plan for this growth.

- Clearly hardware will need to be looked at (can we cope continuing to
use Intel based platform(s)? )
- Also software, are we okay using Postgresql for a 300G database (is
7.2 aimed at this sized undertaking?), How about the os ( can we keep
using Linux or Freebsd ?).

I am informed that the expected number of users is low, so that major
challenges are big queries and the weekly loads. Most of the space used
by the database will be in 1 very big and 1 big table.

Thanks in advance

Mark