Could either be easier by following the trend of getting easier each year or be hard due to the introduction of the formula sheet but it probably won't do much except take away the 1 markers as you said which are just remembering formulas, and adding in more application questions.
Haha so maybe it'll balance out
Though I feel like the 1 markers and stuff don't make up much of the paper, so it's not like they have much to replace in the first place. And also they already have quite a bit of application questions so I'm not sure if the difficulty would actually increase compared to past papers.
They may also be just doing a test run, maybe making it moderately difficult just to see if anything changes. Who knows what they'll choose to do??
And in all honesty, I don't think the formula sheet will help many students in actually excelling more. Students relying on the formula sheet are probably deceiving themselves by studying less for the applications. i.e. there may be a whole group of students studying less or deciding to rely on the formula sheet to do well and thus decide to not study, and I think those people will probably not do so well. They may be the people thinking that the exam will get easier from the formula sheet. Then there are those who may think the exam will get a lot harder (probably most people) and they'll study really hard and do better than normal and join the naturally gifted mathematics kids. I believe the formula sheet will not really help too much INSIDE the exam (preparing for the exam, as outlined next paragraph is different), as the kids that already excel are the ones that don't really need it. Ones relying on it may do somewhat better, unless they rely too much on it. There are so many factors that BOSTES may just want to do a test run to see what will happen - which is not to say they are just being stupid about how they structure the test. But they may make it around the same difficulty, not offsetting the difficulty for the formula sheet.
Also if I recall correctly the whole AIM of this sheet is to reduce rote learning formulas, so reality is the formula sheet is there to help reduce memorisation but actual application will stay the same. So the heart of BOSTES is to reduce rote learning WHICH implies it leads to freeing up more study time for students (not having to memorise formulas but rather can study about how to use the formulas and doing tricky types of questions). It's up to students though to use this time wisely to prepare for it.
Anyway, I guess we'll all find out tomorrow
This is all just speculation and I hope it makes sense and is well reasoned but I could be dead wrong about BOSTES and their paper. Good luck to everyone out there.