I would imagine BiS isn't necessary to get working on your scrips.. However, if you have BiS gathering gear right now, you can probably start gathering the new nodes immediately or with minimal upgrades.. It looks like the Scrip system will be on a timed lockout for gearing up, so you can't just get geared up in a couple days. It will likely take weeks, in which case, investing in BiS right now would be worth the time/money as that will allow you to jump in the market that much quicker.