Ok, so now the curve resides below linear and moves towards it. That isn't sublinear?

Not in mathematical terms. It is superlinear because it always grows faster than linear. However, the degree to which it grows faster than linear decreases. Let's not get too caught up in the terminology though.

The devil will be in details that won't be readily apparent for some time after the fork.

Agree

Does 7 days balance the moving parts of the math, or will it potentially take longer?

1. Maybe. The devs said they adjusted some paramaters so the discontinuity should be small. Let's hope they did a better job than HF19 which took a month or two to rebalance, but we will see.
2. To the extent that behavior changes, that will likely take longer. I wouldn't make any snap judgements on the state of the ecosystem before a few months.