As I understand it, SegWit splits transactions in witness-data and non-witness data. Non-witness data limited to 1MB and non-witness data limited to 3MB, making the theoretical max size of a block 4MB, and the expected block size about 2MB.

If this is incorrect, let me know 🙂

I read one of the worries of the miners is that with SegWit, if we want to double the non-witness limit (1MB => 2MB) in the future, the theoretical max block size will become 8MB (2+6), which will be a strong argument to not increase the non-witness limit.

However, isn't is possible to increase the non-witness limit (for example to 2MB), without increasing the witness limit (in the case the first limit seems to be too small, but the second limit is big enough)?