Unfortunately, no-one can give you a firm prediction about what will happen with grade boundaries, as grade boundaries are set according to lots of factors by the exam boards, and no-one without access to the data exam boards have can tell you what will happen.
I would say that signs probably point to grade boundaries in most subjects going up at least a bit. If you look at what happened with English and maths between the first and second sittings- grade boundaries did go up in both subjects across all exam boards. Also, last year, there was some criticism in the press last year about very low grade boundaries in some subjects. However, we don't have much data to go on!
However, if there was a particular subject/paper that all students found really hard, exam board won't want to have to fail a disproportionate number of students, so in this subject grade boundaries won't go up, and could even go down.
I understand it's difficult waiting for results, but this probably isn't worth worrying about- it's better to find things to do to distract yourself, or focus on things you can control- e.g. coming up with a plan B for worst case scenario results.