Make sure to read the letter from the 12 heads rather than just the press coverage, as some important (positive!) aspects are not covered well by the newspapers - link:
www.fhs-sw1.org.uk/userfiles/francishollandmvc/Documents/Press/Consortium%20Statement%2010%2010%202017.pdf
I see that the new test is CAT rather than simply VR. I am not an expert, but is not a CAT test likely to be reasonably robust gauge of underlying ability and potential future attainment - and already in use, in some form, as a pre-test, by several leading secondary schools?
The letter hints that the consortium is hoping to attract co-ed and boys schools as members in the future, which I really welcome, as one of the major "stress-drivers" for kids (and parents!) is having to prepare for and sit a handful of different tests, with different formats, in different locations, on different days, each being stressful and requiring time off for both children and adults. The consortium is already a life-saver in easing applications to several schools for girls (only), and broadening this to other schools would be brilliant.
The change might help limit (but will far from stop) tutoring - if the CATs are accepted by most parents as mostly measuring real underlying ability i.e. that extra preparation has very little impact on the score. It might also help even out the playing field between children from state primaries vs. private preps. (And it could also be that the fastest-spinning hamster wheels - also called academic preps - will have less appeal to parents of moderately academic kids if these schools are seen as less effective preparation for a CAT test than they currently are for the tests that mostly measure current attainment.
I really hope the test actually will measure ability as opposed to speed, though. My impression is that current (superselective) grammar tests are mostly speed tests where endless practice is essential to get quick enough to be able to get through to the end of the test within the time constraint - not to mention to recognise question types and learn how to crack them. This is a pitfall to avoid when designing the test.
Interviews are already being used by all these schools. I have nothing against these being given more weight, as seems to be an implication.
So to me this sounds like it could be a great development - if they get the test design right and especially if they also manage to expand the consortium membership base.