It does change a big thing in my opinion. I was promoted to Wg Cdr without going to ACSC - so were quite a few of my mates. That is, quite simply, not going to happen anymore.
The new SIRIUS system as I read it is:
ACSC + Wg Cdr = good chance of further
ACSC + Sqn Ldr = fair chance of further
No ACSC + Wg Cdr = no chance but a reasonable pension at 55 (and this will no longer happen)
No ACSC + Sqn Ldr = do not pass Go and do no collect £200 - you're f^cked
The B Word