I'd say about RBA 1.5% too. But only potentially half of the...

I'd say about RBA 1.5% too. But only potentially half of the rises above that point get passed onto customers, because it would be something like:
0.1% on balances <$10k, 0.5% on balances >$10k for example, at say RBA 2.0%. So the interest mostly gets paid to people with larger cash balances (which might be half of total client cash).

But it's hardly a worry, because -

1 rate rise - done. Worth $1.9m PA (if client cash stays flat).
There's still about 5 rate rises to go before we have to calculate how much is passed onto clients.

So by RBA 1.6%, we'd be getting $1.9m*6=$11.4m PA extra, compared to RBA 0.1% of the past few years (or maybe clients and client cash will be higher by then).